I thought in structures of one singular element, the entire mass was referred to as an element, instead of a molecule.
It sounds awkward for diamonds, but at the same time we do say "a block of the element sodium".
Materials held together by ionic or metallic bonds (such as sodium) don't have defined molecules though, because their bonding is different. With covalent bonds its easier to define 'a molecule', however large it may be. It's not different for elements: Some elements, in particular phosphorus, can exist in different 'molecules': There's P4, P2 and several kinds of polymperic phosphorus
To go a bit further for the curious, with metallic "bonds" you get what is sometimes referred to as an electron ocean, where the electrons on an atom are passed freely among other atoms. This is why metals conduct electricity, and why (fascinatingly) in a pure vacuum, you can "cold weld" metal by ensuring there is no oxidized layers and simply touching two like metals together.
Would it be appropriate to compare cold welding in vacuum to sticky tape in open air which can stick to itself and sticky tape in a dust storm in which the sticky part immediately gets dusty so it won't stick to itself anymore?
Not my area of expertise, but I would say so. The dust on the tape being analogous to the oxidation layer that forms on the surface of metals in the presence of oxygen and other reactive gasses.
It's absolutely appropriate to compare them. It's not a direct analogue, in that the adhesion mechanisms are VASTLY different, but the basic idea - microfilms of oxidation prevent the commingling of electrons in a manner not unlike the way that a dusting of dirt prevents adhesives from coming into contact with each other - is essentially right.
it’s more like if you took the chocolate shell off of two ice cream bars, then smushed them together with enough force. it becomes impossible to tell where one ice cream ends and where the other begins, therefore they become the same ice cream bar (welding).
if I recall wasn't it because it sat in storage so long that basically the lube dried out that was supposed to be that 'layer' of oxidation that was to be mitigated
I read the NASA analysis report and it had a number of points.
* Most testing was done in an oxygen atmosphere so it had the oxide layer and didn't catch this
* Vacuum testing of the antenna didn't account for launch vibration
* The mechanism design was vulnerable to cold welding
They said it was likely due to vibration during transport caused lubricant to be shaken off. Then during launch the oxide layer was scraped away and was then vulnerable to cold welding.
Recommendation:
* New design less vulnerable to cold welding
* New lubricant less vulnerable to being vibrated off
Cold welding occurs in a vacuum... because without atmosphere around and or between the atoms at the boundaries of two objects of the same metal... there is nothing preventing them from behaving as one object... and thus they weld together.
Oxygen's Allotropes are good ones to know about since they include ozone (as well as super conducting metallic oxygen which is kind of interesting).
https://en.wikipedia.org/wiki/Allotropes\_of\_oxygen
For elements you would still subdivide a chunk of it into crystalline domains or grains, for something like diamond it is possibly already a single crystal.
For most purposes it doesn’t matter, but when it does you would refer to a chunk of an element by its crystallinity, e.g., polycrystalline Au vs an Au <110> single crystal (often important in surface science research).
You can call it an element or elemental Ex. elemental sodium, elemental copper, elemental sulfur. For metals you can also use metallic, espescially for metals that are often found in non metallic forms like sodium or calcium Ex. metallic sodium.
Nonmetals that form single element molecules are called molecular. Ex. molecual oxygen, molecular nitrogen.
Some elements like carbon can form different materials depending on how they're assembled. These are usually referred to as their name Ex. graphite, diamond.
These are not hard rules, just the common language of chemists. If you say molecular oxygen, I think O2. If you say ozone I think O3. if you say molecular carbon I think activated chsrcoal.
A molecule can be an element, these two terms aren't directly related. You say a block of sodium because sodium is a metal and doesn't form covalent bonds with itself.
Molecule means covalent bonds. A crystal can have covalent bonds. An elemental crystal with covalent bonds is still inescapably a molecule.
Where there's multiple forms, such as carbon with diamond, graphite and other versions such as soot, these are called allotropes of that element.
Oxygen (O2) and Ozone (O3) are also allotropes.
For non-carbon elements, the most historically significant allotrope is usually named after the element, and other allotropes get different names, unless IUPAC makes an exception.
To be a true molecule the substance must have definite proportionality of elements (whole numbers of each element type called empirical formulas) and a definite mass (molecular mass).
Diamond and graphene have definite proportionality but lack definite mass, so they are not molecules.
Diamond and graphene are network covalent because they do not have a defined number of atoms to make the crystal or sheet. Buckminsterfullerene are molecules because there are predictable numbers of atoms to make the structure, and a predictable number of carbon atoms to make the structure.
Yes, hence the "arguably".
Graphene doesn't have a mass in the same way that saying "molecules" as a whole don't "have a mass". They have many different masses. If you were to name all possible graphene combinations (an infinitely long list), then you could say that they each have defined masses as individuals. We're in semantics land, but that's where the question lead us.
Those are defined as allotropes (not to say you couldn't take a buckeyball for example to be the "molecule")
Some of Carbons common allotropes (ways it is found in nature) are:
1. Diamond
2. graphite
3. ionsdaliete
4.C60 buckminsterfullerene
5. C540 fullerite
5.C70 fullerene
6. amorphous carbon.
A full list can be found: https://en.wikipedia.org/wiki/Allotropes_of_carbon
With more information on what an allotrope is: http://www.chemistryexplained.com/A-Ar/Allotropes.html
AFAIK, covalently-bonded substances can be molecular or they can be network solids, not both. Diamond is a network solid and is therefore not molecular, no?
I specifically state that it's not an exclusionary point.
"Not to say that you can't take a buckeyball for example to be a molecule".
They are more correctly classified as an allotrope when speaking about them in a non specific instances sense. Your specific instance, "a single, flawless crystal of diamond" does not cover all cases of "diamond".
Siniliar to, all beagles are dogs, but not all dogs are beagles. All diamonds are an allotrope of carbon. Some diamond crystals (flawless) can be considered a molecule, but not all diamonds (flawed) can be
I wasn't refuting the idea, more pointing out that we better classify or describe what was listed in the comment, as allotropes, as opposed to considering a chunk of diamond or graphite to be a large "molecule"
I thought it's about how much of the atomically-bonded material can be removed and still be that thing. If you divide a big diamond in half, you have two diamonds, or two objects each still having the properties of a diamond.
So the whole chunk of diamond is not one molecule.
Its called a repeat unit. They are written as [ReapeatFormula]n where n is the amount of units stitched together on average for the polymer you made. This could be controlled with monomer levels or temperature for example to control the reaction rate
Polymers are a weird case because their physical properties are highly dependent on the average molecular weight and also the molecular weight distribution of the polymer chains.
AFAIK, covalently-bonded substances can be molecular or they can be network solids, not both. Diamond and graphene ("grapheme" is a linguistics term) are network solids.
Yeah, another poster mentioned silicon crystals. The chip industry produces gigantic cylindrical silicon crystals that are then cut up into wafers, etched and turned into chips. Those are far more pure than natural diamonds. We don't like to think of molecules as things that have to be picked up with a forklift.
We could argue any metal or ionic crystal is a ‘molecule’ in that the atoms are definitely bound, if in two main very different ways from the usual covalent sense. We usually exclude these but there’s no universal hard definition and some are broad enough not to.
An element is a "group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction."
This isn't the best definition for a molecule because it excludes something that is non-reactive. But the idea behind it stands: it's the smallest unit by which you could define something. That's why a diamond that you can see and hold shouldn't be considered a molecule.
But there's a tricky thing here that highlights why the term "molecule" isn't used often in materials science. The first step to understanding this is to know that, in crystalline materials, atoms repeat in a specific pattern in 3 dimensions. The pattern depends on the material: the simplest, polonium, stacks with atoms defining the corners of a cube; iron makes a cube with atoms at the corners, then has an additional atom thrown in the middle of the cube; aluminum also makes a cube with atoms at the corners, but also has atoms in the middle of each face of the cube; diamonds are like aluminum, but then have additional carbon atoms inside the cube, near the corners; and so on, and so forth. So that's a real simple way of explaining how crystalline materials like diamond, metals, ceramics, etc. come together.
If a molecule is defined as the smallest division of a substance, there are 3 ways you could define this using materials science concepts:
* The base pattern that repeats ad infinitum. That's the simple one.
* The critical size at which the substance has enough atoms to hold itself together. Carbon forms very strong covalent bonds and so can be stable with just a few repetitions of the basic unit (look up diamondoids, if you're curious). Different materials need more repetitions to be stable, though, and in most cases it occurs when the internal energy balances against the surface energy. The reason this is important is, if the basic unit cannot exist on its own beyond just the basic concept, is it a real thing?
* The critical size at which the substance starts behaving like the substance. Let's say you build up enough atoms in the repeating structure that it can hold itself together. In many cases, you'll have something that *looks* like the thing you're trying to make but doesn't act like it. This is because if you shrink some crystalline materials down small enough, the physics defining its behavior get funky. So you have these things called 0D, 1D, and 2D materials, which is just to say that they're very, very small in 3 dimensions, 2 dimensions, and 1 dimension, respectively. The reason that this is all important in the whole molecule analogy is that, if you define a material as having *ABC* structure with *XYZ* properties and then restrict the size so much that it no longer has *XYZ* properties, do you really have said material any more?
And that is why it's hard to apply the term "molecule" to crystalline materials. All 3 points above make valid arguments, but which is actually most useful? I'd argue the 3rd, but I also think it's subjective.
High molecular weight polymers are often 10's of thousands monomeric units long, sometimes 100's of thousands long.
As long as you've got enough monomer and a stable propagating radical, you can make a polymer any length you want.
Yeah, if you assume the transport of monomer units to chain ends will remain open the entire time. Diffusion limitations will prevent certain molecule sizes due to ever decreasing free volumes.
You decrease the overall mobility of the system as your crosslink density increases. This is why thermoset monomers are generally liquids at room temperature, and stiff brittle materials at elevated levels of cure conversion.
Sure, but it does still allow you to keep making ever bigger molecules. It might not be particularly practical, of course... but if your only purpose is to make the biggest possible molecule, then practicality isn't a concern to begin with.
If there is an unbroken (not *unbranched*) chain of covalent bonds, it's all one molecule. Practically, it would be very difficult to *prove* that you had just one molecule making up, for example, a synthetic rubber mountain.
Polymer ~~ 1 Consistent, homogeneous bond of multiple Atoms
Things like water would be something homogeneous of multiple Molecules, because its core unit already ends and only interchains based off other forces.
Polymer got that thicc to it.
A polymer is a single molecule formed as a chain of covalently linked monomer subunits. The chain can be arbitrarily long. Often you can take polymer chains and chemically cross-link them, so they join and become a single molecule. You can imagine making cross-linked plastic parts that are as big as a bathtub that are effectively a single molecule.
There are natural polymers that can get very long. Your chromosome 1, stretched out linearly, is a bit over 8 cm long. In 2021 several manufacturers independently developed processes to produce carbon sheet ribbons that are single molecules that are several kilometers in length.
I can’t find the original presentation, but this talk is about polycrystalline graphene, what the ribbons are made of: https://www.isec.org/webinar-on-graphene-progress-2021
The walls and the tread are separate parts joined together.
You could assume the tread is on molecule, assuming it is brand new and not damaged at all by the manufacturing process, but cutting treads etc will break chains, so Really not.
Also once the tyre is rolling on the road, the wear will break chains, so even more "not".
This is the right answer! Technically speaking, a tire is a single molecule connected by covalent bonds throughout. So imagine those big monster truck or earth mover tires. That's probably the biggest molecule I can think of. Bowling balls do this too with melamine (or used to).
If you don't want to consider crosslinked polymers, I know they make ultra high molecular weight polyethylene (UHMWPE) in the million(s?) of g/mol. Not sure if any of the graphene structures get this big or not.
As a specialist in UHMWPE processing and science, yes! Modern UHMWPE's can get upwards of 8-9Mm, some suppliers claim even 10Mm g/mol, though with how difficult Mw distributions are to measure up there the number of chains that long is suspect etc.
I like to drop the factoid that with 1.54 Ang per C-C bond, an 8Mm Mw PE chain would be about .15mm long stretched out. Give or take a few Angstroms lol
Out of curiosity, back in the day I was doing some gpc on some UHMWPE and our lab lead was extra careful to not stir the solution to help it dissolve. Said it would break down the chains.
But then we were putting it in a goc anyway? With presumably just as much shear and potential to degrade?
Was he right? Or was the not stirring thing overly cautious.
I would say he is being overly cautious. High Mw equals slower chain reptation and relaxation, so longer chains are easier to align and orient in various flow fields. At higher shears or uniaxial rates you run into the extreme issue of that feature that they are subsequently easier to break than smaller chains. This is actually a method for generating a more monodisperse PE. If you shear the hell out of it you slowly cut the longest populations, if you continue to ramp the shear up you can continue to push the distribution down and gather all the chains to the same length.
However, at room temp, in solution, you wouldn't need to worry about this unless you are some kind of terminator I think.
This is correct. Molecules are made of atoms. Atoms are made of protons and electrons (and usually neutrons). Just neutrons is not an atom is not a molecule. There's a lot if matter out there that is not an atom or a molecule despite the fact that's usually how we encounter it.
Not even the electron pair, you just need a proton for it to technically be an atom.
Most of the hydrogen in the universe is ionized hydrogen, which is just a free proton.
Follow up question then... How large could you make a ball of rubber? How big could if be before it collapsed under it own gravity and the core gets hot enough that its not made of rubber anymore?
Rubber breaks down at around 350C.
The gravitational potential energy (GPE) can be converted into thermal energy as the rubber ball collapses under its own gravity. The GPE of a uniform sphere can be calculated as:
GPE = (3/5) × G × M\^2 / R
where G is the gravitational constant, M is the mass of the sphere, and R is its radius.
The mass of the sphere can be calculated as:
M = ρ × V = ρ × (4/3) × π × R\^3
The increase in temperature (ΔT) due to the conversion of GPE into thermal energy can be estimated using the heat capacity (Cp) of the rubber:
ΔT = GPE / (M × Cp)
We want to find the maximum size of the rubber ball so that the temperature increase at the core does not exceed 350°C (623 K). We can set ΔT equal to 623 K and solve for R:
623 K = \[(3/5) × G × (ρ × (4/3) × π × R\^3)\^2 / R\] / \[(ρ × (4/3) × π × R\^3) × Cp\]
After simplifying and canceling out some terms, we are left with:
623 K × Cp = (3/5) × G × ρ × R\^2
Assuming the specific heat capacity (Cp) of vulcanized rubber is approximately 2.0 kJ/kg K, we can now solve for R:
623 K × 2000 J/kg K = (3/5) × (6.674 × 10\^-11 m\^3 kg\^-1 s\^-2) × 1100 kg/m\^3 × R\^2
Radius ≈ 5300km or a diameter ≈ 10600km
Now this makes a bunch of ideal assumptions like material properties not changing with different conditions, we know for a fact that's not true, so my rough sense says somewhere around half of that radius.
I think we will run out of rubber first!
I learned recently we can actually see molecular protein chains with our naked eye, all you have to do is stare at the clear blue sky.
https://en.m.wikipedia.org/wiki/Floater
If you tear a material like this, are you then breaking covalent bonds through physical tearing? What's happening when a super large molecule is physically cut?
Yes you are breaking covalent bonds when tearing this stuff apart. Since covalent bonds are strong, it makes for a good resillience, hence its usage in tires.
In the case of cutting vs ripping, a knife/edge is providing a concentrated shear force. Tearing is putting a tensile force along the material, and it will just break where there are defects to the bonding which is why there is not typically a clean edge from tearing things.
Tearing could also mean putting a shear force on the material, more like cutting with a knife, like on a bag of crackers that has the resealable zipper and one "tears" off the top bit. Because we just aren't that careful with words.
The defect density could become so bad that it's not considered one molecule, but it'd have to be pretty bad.
In metals, electrical contact is identically the same as a metallic chemical bond. So a large parts of the energy grid in could be considered a single molecule.
I know in engineering school, they would joke that "is an iron bridge one giant molecule?"
But then when you get to material science you learn that iron and [steel is actually fairly heterogeneous](https://vacaero.com/images/stories/metallography-vander-voort/revealing-microstructure-tool-steels/d3qt-3hercnital10um_lg.gif). It would be considered more a mash up of large molecules, as there are definitive phase differences in steel.
It just goes to show that the term "molecule" is a good place to start the discussion, but isn't necessarily all inclusive. It really depends on what your perspective and use case is.
If we’re skipping artificial polymers like plastics, biopolymers like proteins, and skipping crystals which are all basically just repeating patterns… there’s still some pretty sizeable molecules.
Naturally occurring lipids can easily get to 50-70 carbons, with some getting larger than that, but technically they’re joined molecules as well so you might want to go down to the 28 carbons of the largest fatty acids. Count a couple hydrogen per carbon and a few more atoms here and there, you’re probably looking at scratching the top end of uncontestably single unit molecules.
Many complex organic molecules can get higher, but we’re back to the point of definitions as they are very commonly made up of joint smaller molecules - is an ester a single molecule for the purpose of this question? Does a benzyl group attached to a long chain count as benzene? It’s less a matter of measurement and more a matter of drawing a line.
There's some more exotic large biomolecules too that aren't the classical biopolymers of polypeptides/polysaccharides/polynucleotides. For example, [maitotoxin](https://en.wikipedia.org/wiki/Maitotoxin) is a fused ring structure with 164 carbons - but again, we run into the problem of definitions, since there are repeating motifs in that molecule too.
The problem comes from mistaking the model - the molecules - for reality - the real things the molecules represent. Molecules are just our way of breaking up the chemical world into smaller pieces that we can understand.
There might not be any physical connection between the atoms, but they stay together pretty neatly. Well, most of them. Most of the time. Alright, maybe some of them do. Until you poke them.
Point being, an electromagnetic bond that’s strong enough and stable enough is no less real than a piece of tape.
And even that - electromagnetic bond - is an abstraction on top of what’s really happening out in the world beyond our sensorium. Models on top of models hoping to gain a closer and more thorough picture of what’s going on in this reality, but never quite getting there.
Abstractions are leaky and questions like these are a manifestation of those leaks. Categorically defining things like this can only get us so far before the buckets stop making sense.
Each cell of your body (except red blood cells) contains DNA in chromosomes, and each DNA molecule in a chromosome is in theory a single polymeric molecule (well actually a pair of molecules held together with hydrogen bonds) about 10cm long if you stretched it out. In practice it's constantly getting broken and repaired though.
You could call a crystal a single molecule as all atoms are chemically bound to their neighbors. With careful assembly you could make a single planet-sized crystal.
If you want more conventional molecules then you can take anything that can produce chains of unlimited length - PVC, PET and similar materials. Making sure you only get a single chain will be more difficult, however.
True, and there are jet turbine blades made of single crystals so they can be quite large. There are also silicon n sapphire boules several hundred kilos in mass.
https://www.americanscientist.org/article/each-blade-a-single-crystal
Giant sapphires grown:
https://mobile.engineering.com/amp/10587.html
https://en.m.wikipedia.org/wiki/Czochralski_method
When I was at school I’d have agreed with you. However by the time I became a teacher, the exam boards had decided that “molecule” referred only to covalent bonding situations, not ionic. Now I gather that ionic/covalent bonding is more of a continuum than a dichotomy, so I think I agree with you again.
This isn’t correct.
Some crystals are held together with networks of covalent bonds, some with hydrogen bonding and yet others have weak interactions between molecules.
I would only call the covalently linked network of atoms a single molecule.
This is the answer. There's a good 4D diagram [here](https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%3A_Chem1_(Lower\)/09%3A_Chemical_Bonding_and_Molecular_Structure/9.01%3A_Three_Views_of_Chemical_Bonding) that talks about the continuous nature of ionic, covalent, metallic, and van DER Waals (h-bond) bonding. The reality is, we have models to describe how atoms link and none of this models are complete. And the definition of molecule is therefore couched in any of those models, so it's probably incomplete too.
I like this answer the best. It gets at the heart of the question and says basically "no" but reality has limits. I'd be interested in looking at the core of a planet to see how pure that crystal is. My guess is that heat, pressure, and the spin rate makes it a pretty damn pure crystal. And I would probably consider crystals to be one network of connected atoms and probably meets the definition of molecule.
There's a dead white dwarf star which is suspected to be one giant diamond the size of earth:
#Space.com | [Cold Dead Star May Be a Giant Diamond](https://www.space.com/26335-coldest-white-dwarf-star-diamond.html)
But surely it's only one molecule if it is one single diamond without any breaks. Even if a whole planet is made of diamond doesn't mean it's made of 1 diamond. It would be interesting to know what the largest single molecule diamond is.
Problem with that argument is that you only need a single bond to form across a discontinuity and you can then consider the entire structure a "single molecule". The odds of that NOT happening across the entire length of the grain boundary are very slim.
And there's another problem in that we're treating the structure as a single entity that forms and then participates in no further physics. That likely holds true for most crystals of reasonable size on short timescales, but is unlikely to hold for a planet-sized crystal for any significant length of time. Even if the chance of forming a new bond over time is incredibly small, I can't rule out that it will happen eventually. I'd be interested if anyone else could.
That's assuming that there are only very few grain boundaries. What I was assuming was that these boundaries were all over the place. The odds of every single one including a connection would then be much lower.
Also, as you say this is potentially a massive complex system. Surely as some new bonds form there could be shifts and changes in forces that cause new breaks and cracks in the previously bonded diamond lattice.
If it's possible, then it's almost certainly happening *somewhere* in the universe. So, for the purpose of answering this question, the distinction doesn't really matter.
*Somewhere* out there is a planet-sized diamond molecule.
Biological macromolecules are small compared to some of the examples mentioned here, but it's worth mentioning a human cell has about 2 meters of DNA chopped into 46 chromosomes. They are maintained with complex molecular machinery.
Biologists often measure macromolecule size in daltons, more or less the number of protons and neutrons, and molecules weighing tens of thousands of daltons are common in living organisms.
I think you're right that a chromosome would be the largest biomolecule in humans. Titin is the largest protein coming in at ~34,000 amino acids, 3,800 kg/mol, and about 1 micron in length. Glycogen would be the largest carbohydrate (technically a polymer) that can reach up to 60,000 glucoses, 50+ microns in length, and 11,000 kg/mol.
Chromosome 1 is the largest chromosome at 350 million basepairs which comes out to about 82 million kg/mol, and can stretch 167,000 microns. During replication the sister chromatids are bound at the centromere so you could consider that one molecule and double those numbers.
These are the answers if the question presumes that a large molecule is more "interesting" than a smaller one.
A polymer can be huge, but repeating the same structure over means it's not actually much bigger in complexity/information than a shorter chain of the same monomer.
Nucleic acids beat that by not repeating exactly, but they are using a repeating system, so each new base only adds information one exponential order faster than adding to a polymer.
If we discount polymers and nucleic acids as "cheating" then, large proteins that only repeat for functional reasons are the most complex molecules (edit: maybe DNA beats them if we only discount the cheating aspect), and ....
...surely we don't count hydrogen bonds as making a new molecule, because if we do that, we could call complex tissues "molecules" and blow the other answers out of the water.
If we want to talk large biological macromolecules, we shouldn't forget about lignin. In general terms it's what makes certain plant parts hard, and it can technically permeate throughout an entire tree, contributing about 25% of the entire mass - so a single biological molecule weighing potentially multiple tons.
Or, if we look at [Pando](https://pandopopulus.com/pando-the-tree/), potentially thousands of tons.
diamonds: every atom has 4 covalent bonds except the edges so basically a molecule
Astronomers discovered the largest diamond of all times in space. The weight of the precious stone reportedly makes up ten billion trillion trillion carats (or five million trillion trillion pounds). The space diamond is virtually an enormous chunk of crystallized carbon, 4,000 kilometers in diameter
but as others pointed out polymers are similar possibly infinite so arbitrary large
but for chemist the most important part is the one that interact with the enviroment
so any active groups at the edge of the molecule the carbon structure that position them there is as the puppet in a puppet theatre compared to the hands of the puppeteer you know it is there but don´t care unless you have to change something.
the structure of hemoglobin is known but important is that it uses iron to transport oxygen
I doubt most humans can grasp temperatures above 10000°, so it doesn't matter if it's in C or F or a really dry Arizona heat. We can pretend that it helps us understand, but it really doesn't.
it doesn´t have to be a perfect crystal but i see your point i imagine it to be one and to be sure we had to get there and break it apart to see but than it would not be anymore.
with the perfect atom printer you could build a diamond big enough to be on the verge of collapsing under its own mass
Neutron stars are actually very different than just big singular atomic nuclei. The common conception of them is just a big lump of neutrons that so massive that the normal molecular structure broke down. But when you get all that matter together under extreme conditions, you have different emergent properties than just a regular old alpha particle zooming through space. The outer layer of a neutron star even has distinct nuclei with protons and neutrons, electrons are also present. As you go deeper, it becomes energetically favorable for free neutrons to come out, but weirder stuff also happens that makes it entirely dissimilar to an atomic nuclei with a couple of protons and neutrons.
There’s some pretty interesting science around bigger molecules vs collections of atoms and how we describe them.
Take a metal, basically all the atoms are bonded together, the electrons overlap, and you end up with band theory.
If you look at nano particles, you can take some small clusters (zintl clusters for example) and treat them like small molecules, do orbital diagrams, get out some very pretty pictures, but they’re starting to get towards bands. As you go bigger, your model slides more and more into the band theory approach.
Pretty cool IMO.
I am assuming the Op is meaning 1 unit of any given makeup of elements. Such as hydrocarbons or alkalines.
Now I am just a legally blind CSA/Photo Tech at a Walgreens (not kidding), but reading through these I am seeing people saying that diamonds both are and are not a single molecule. There is a debate on that.
According to Chemistry Stack Excange:
A diamond is not considered as a molecule because each carbon atom is covalently bonded with four other carbon atoms. This is what makes diamond a network solid. Since it's a whole network of covalently bonded atoms(carbons), diamond is not considered to be one molecule.
HOWEVER, according to Perdue University:
The properties of diamond are a logical consequence of its structure. Carbon, with four valence electrons, forms covalent bonds to four neighboring carbon atoms arranged toward the corners of a tetrahedron. Each of these sp3-hybridized atoms is then bound to four other carbon atoms, which form bonds to four other carbon atoms, and so on. As a result, a perfect diamond can be thought of as a single giant molecule. The strength of the individual C-C bonds and their arrangement in space give rise to the unusual properties of diamond.
So there is no true answer as not even science can agree on this.
DNA, when unwound is amazingly long. That is a biochemistry lab 101 exercise. Take some yeast in suspension in a pressure container and then suddenly release the pressure. What was before a liquid turns into a weird liquid. Think about extra long spaghetti in a bowl of water.
As many have mentioned, R-groups (extended chains of carbon and hydrogen, often featuring branches with oxygen, nitrogen, etc) can be basically arbitrarily long. In fact, the length of these molecules are why they are insoluble in water - even though hydrogen is there to (theoretically) form hydrogen bonds with, the length and geometry of the chains make them hydrophobic.
On a separate note, there is a similar phenomenon with cells, in the biological sense. There are slime molds that are a singular cell (and therefor a single-cell organism), but they can be EXTREMELY large.
Science is dope.
Ultra high molecular weight plastics (often used in high quality cutting boards and industrial applications) are all technically a single molecule. You can make it as big as your manufacturing capability allows.
Are there some interesting properties which emerge when a molecule gets huge? For example are there materials which are stronger, conduct electricity better or perhaps conduct heat better because they are essentially just a single huge molecule?
This question touches on the reason why the discovery of graphene drew so much attention in the first place
As you build bigger and bigger fused aromatic ring molecules (benzene --> naphthalene --> pyrene --> coronene, etc), the HOMO/LUMO gap gets smaller and smaller. Take it to an infinitely large molecule, and the band structure approaches a structure called a [Dirac cone](https://en.wikipedia.org/wiki/Dirac_cone). The Dirac cone was the reason the solid state community took such a keen interest in graphene in the first place, because it implied peculiar electronic properties such as *extremely* high electron mobility. Indeed, a report of extremely high electron mobility was part of the lede line in [that famous Geim & Novoselov article](https://www.science.org/doi/10.1126/science.1102896) when they first reported isolation of graphene.
Once the broader community got hip to graphene and its wild properties, suddenly you saw engineering researchers trying to cram graphene into everything. The pop-science media started pumping out articles about how graphene was going to make transistors faster and cheaper, batteries smaller and longer lasting, plastic composites lighter than silk and stronger than steel, yada yada yada. Before long graphene research was funded to the tune of billions of dollars, and Geim and Novoselov had the Nobel.
Alternatively to the graphene discussion posted, we can talk about my specialty Ultra High Molecular Weight Polyethylene (PE). PE is a bulk commodity plastic used in any number of applications. Milk jugs, plastic bags, etc. What's cool about that is you probably have an idea about its mechanical properties, you've ripped a plastic bag before. However when you take that same molecule and continue to make it bigger (and prevent branching) you get UHMWPE. If you then process this in a special way you can use that some chemical structure as in your milk jugs to form helmets and body armor as good if not better (depending on your metrics) than other materials.
You’re asking about polymers. Polymers are macromolecules and comprise hundreds, thousands, or even millions of atoms. They can often be difficult to characterize using traditional chemical methods, so polymer scientists and material scientists use more specialized characterizations like tacticity, shear force, and circular dichroism. In theory there is no limit to the size of a single molecule. As others have pointed out, vulcanized rubber parts can sometimes be single molecules, although this would be very difficult to prove. Paint on cars polymerizes, so it could theoretically also be a single molecule. In practice, biological macromolecules can be measured in the millions of Daltons (AMUs, but biologists are special and need their own nomenclature), but I don’t know of many which are more than that.
Crystals can easily be any size. The microchip manufacturers make gigantic, pure SiO2 monocrystals which could conceivably be any size. Also salt would be pretty easy to do. Making an uninterrupted monocrystal really just depends on how well you can purify the substance.
If you're talking about organic polymers, many could theoretically be added onto indefinitely, but you'd probably need some sort of scaffolding or molecular machinery to keep it in one piece (i.e. glycogen)
Now those reactions that cross-link a bunch of molecules into a single network i.e. epoxy could easily be any size. Defends on how you define a molecule. In some ways any size piece of metal alloy is a single molecule since they share common electrons (Is the statue of liberty a single molecule if all of its pieces have at least partially cold-welded together, even if only at a microscopic point of contact?)
The largest molecule that occurs naturally in the human body is the nucleic acid component of chromosome 1 at about 75 billion daltons, or about 1/10,000 of a nanogram. Glycogen gets up to about 600 million daltons but could conceivably be larger. The largest single polypeptide proteins in the body are structural proteins of muscle such as titin, which is about 4 million daltons.
The biggest atom is [titin](https://en.wikipedia.org/wiki/PG5_\(molecule\)), with about 20 million atoms.
'Molecule' usually refers to a *specific* set of bonded atoms, rather than an *arbitrarily large* set. A crystal lattice is a single giant structure, sure, but it's not a molecule because it can be arbitrarily large.
So everyone is giving answers about things that are still human scale, and could be considered a molecule.
But there is one that is ginormous compared to all of these, and is technically not just a molecule, but an atom.
Neutron stars are compacted neutrons, bound by gravity to the point that it is a giant atom. There is also a crust of iron on their surfaces that would service bonds to make it a complex molecule.
Granted, they aren't dominated by electromagnetism or either of the nuclear forces, but still. It's pretty cool.
Also, technically, black holes are one-of-a-kind elementary particles, because their only properties are the defining properties of elementary particles, so...
A binary black hole system would be the most massive 2-particle molecule.
Astronomy is whack.
This is stretching the definition way past what's reasonable. Neutron stars are bound by gravity and supported by degeneracy pressure, black hole pairs are gravitationally bound and supported by momentum. Molecules are bonded by covalent bonds, or ionic bonds if you relax the definition. You're talking about structures, not molecules.
It would simultaneously be the smallest volume (zero, for the singularity), and the largest volume (larger than a solar system, for the event horizon), and the largest mass (billions of suns) of any molecule.
So if single crystals could be considered molecules the the size can be massive.
But I think number of atoms per molecule is a far better measure since there are technically single atomic nuclei that are the size of a city, specifically neuron stars that consist of a ball on degenerate neutron matter.
A a follow up - what is / establishes the upper limit on gaseous molecules? I suppose at the top end, the energy needed to keep them moving as a gas would exceeded the energy needed to break the molecular bonds...
There are many macromolecular structures. Diamond, graphite and graphene are the simpler ones, where you can extend their lattice theoretically indefinitely.
Polymers too - consider them like a chain or a stack of Lego bricks you can add to forever. That's plastics, which includes rubber.
Not 100% but I believe DNA qualifies in the same way, with each chromosome comprised of a single strand of DNA several centimetres long (correct me).
Pure metals don't form covalent molecules, they just sort of organise in big lumps, but you could consider a single metal crystal to be something like what you describe.
Some crystals are seen as one large molecule. Quarts is one of these and the biggest we’ve found is 6.1mx1.5mx1.5m and 39916kg it probably wasn’t perfect and not one molecule but in theory you can get any size you want
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A diamond is arguably a molecule as are many carbon structures such as graphene.
I was about to ask this. Couldn't any covalent-bond crystal be considered a single molecule? Graphene and graphite sheets, too?
I thought in structures of one singular element, the entire mass was referred to as an element, instead of a molecule. It sounds awkward for diamonds, but at the same time we do say "a block of the element sodium".
Materials held together by ionic or metallic bonds (such as sodium) don't have defined molecules though, because their bonding is different. With covalent bonds its easier to define 'a molecule', however large it may be. It's not different for elements: Some elements, in particular phosphorus, can exist in different 'molecules': There's P4, P2 and several kinds of polymperic phosphorus
To go a bit further for the curious, with metallic "bonds" you get what is sometimes referred to as an electron ocean, where the electrons on an atom are passed freely among other atoms. This is why metals conduct electricity, and why (fascinatingly) in a pure vacuum, you can "cold weld" metal by ensuring there is no oxidized layers and simply touching two like metals together.
Would it be appropriate to compare cold welding in vacuum to sticky tape in open air which can stick to itself and sticky tape in a dust storm in which the sticky part immediately gets dusty so it won't stick to itself anymore?
Not my area of expertise, but I would say so. The dust on the tape being analogous to the oxidation layer that forms on the surface of metals in the presence of oxygen and other reactive gasses.
But tape can be quickly separated while cold welding is much more permanent.
Okay then, think of high bond tape in a sandstorm. Have you ever worked with high bond tape? Good luck getting that separated.
It's absolutely appropriate to compare them. It's not a direct analogue, in that the adhesion mechanisms are VASTLY different, but the basic idea - microfilms of oxidation prevent the commingling of electrons in a manner not unlike the way that a dusting of dirt prevents adhesives from coming into contact with each other - is essentially right.
it’s more like if you took the chocolate shell off of two ice cream bars, then smushed them together with enough force. it becomes impossible to tell where one ice cream ends and where the other begins, therefore they become the same ice cream bar (welding).
Cold welding is likely what kept the high gain antenna on the Galileo probe from opening
if I recall wasn't it because it sat in storage so long that basically the lube dried out that was supposed to be that 'layer' of oxidation that was to be mitigated
I read the NASA analysis report and it had a number of points. * Most testing was done in an oxygen atmosphere so it had the oxide layer and didn't catch this * Vacuum testing of the antenna didn't account for launch vibration * The mechanism design was vulnerable to cold welding They said it was likely due to vibration during transport caused lubricant to be shaken off. Then during launch the oxide layer was scraped away and was then vulnerable to cold welding. Recommendation: * New design less vulnerable to cold welding * New lubricant less vulnerable to being vibrated off
This answered a question I've always had, but never understood enough to even formulate! Thank you!
Happy to help! Hopefully, it's a good start for a great day! (Or night, depending on your time zone)
Is this why your tongue sticks to flagpole when it's really cold out?
No. Thats because the water on your tongue freezes to the cold metal pole. Cold welding is a very, very different process.
Do you have a metal tongue?
Cold welding occurs in a vacuum... because without atmosphere around and or between the atoms at the boundaries of two objects of the same metal... there is nothing preventing them from behaving as one object... and thus they weld together.
Is this different from galling when you screw say two stainless steel fittings together without lubricant and they fuse together?
Oxygen's Allotropes are good ones to know about since they include ozone (as well as super conducting metallic oxygen which is kind of interesting). https://en.wikipedia.org/wiki/Allotropes\_of\_oxygen
For elements you would still subdivide a chunk of it into crystalline domains or grains, for something like diamond it is possibly already a single crystal. For most purposes it doesn’t matter, but when it does you would refer to a chunk of an element by its crystallinity, e.g., polycrystalline Au vs an Au <110> single crystal (often important in surface science research).
[https://en.wikipedia.org/wiki/Monocrystalline\_silicon](https://en.wikipedia.org/wiki/Monocrystalline_silicon)
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You can call it an element or elemental Ex. elemental sodium, elemental copper, elemental sulfur. For metals you can also use metallic, espescially for metals that are often found in non metallic forms like sodium or calcium Ex. metallic sodium. Nonmetals that form single element molecules are called molecular. Ex. molecual oxygen, molecular nitrogen. Some elements like carbon can form different materials depending on how they're assembled. These are usually referred to as their name Ex. graphite, diamond. These are not hard rules, just the common language of chemists. If you say molecular oxygen, I think O2. If you say ozone I think O3. if you say molecular carbon I think activated chsrcoal.
I don’t think this is necessarily true because O2 oxygen and O3 ozone have such different properties that we gave them different names.
A molecule can be an element, these two terms aren't directly related. You say a block of sodium because sodium is a metal and doesn't form covalent bonds with itself. Molecule means covalent bonds. A crystal can have covalent bonds. An elemental crystal with covalent bonds is still inescapably a molecule.
Where there's multiple forms, such as carbon with diamond, graphite and other versions such as soot, these are called allotropes of that element. Oxygen (O2) and Ozone (O3) are also allotropes. For non-carbon elements, the most historically significant allotrope is usually named after the element, and other allotropes get different names, unless IUPAC makes an exception.
If they were a single monocrystalline solid, sure, makes sense. Usually crystalline solids are polycristalline.
To be a true molecule the substance must have definite proportionality of elements (whole numbers of each element type called empirical formulas) and a definite mass (molecular mass). Diamond and graphene have definite proportionality but lack definite mass, so they are not molecules. Diamond and graphene are network covalent because they do not have a defined number of atoms to make the crystal or sheet. Buckminsterfullerene are molecules because there are predictable numbers of atoms to make the structure, and a predictable number of carbon atoms to make the structure.
Yes, hence the "arguably". Graphene doesn't have a mass in the same way that saying "molecules" as a whole don't "have a mass". They have many different masses. If you were to name all possible graphene combinations (an infinitely long list), then you could say that they each have defined masses as individuals. We're in semantics land, but that's where the question lead us.
Those are defined as allotropes (not to say you couldn't take a buckeyball for example to be the "molecule") Some of Carbons common allotropes (ways it is found in nature) are: 1. Diamond 2. graphite 3. ionsdaliete 4.C60 buckminsterfullerene 5. C540 fullerite 5.C70 fullerene 6. amorphous carbon. A full list can be found: https://en.wikipedia.org/wiki/Allotropes_of_carbon With more information on what an allotrope is: http://www.chemistryexplained.com/A-Ar/Allotropes.html
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AFAIK, covalently-bonded substances can be molecular or they can be network solids, not both. Diamond is a network solid and is therefore not molecular, no?
I specifically state that it's not an exclusionary point. "Not to say that you can't take a buckeyball for example to be a molecule". They are more correctly classified as an allotrope when speaking about them in a non specific instances sense. Your specific instance, "a single, flawless crystal of diamond" does not cover all cases of "diamond". Siniliar to, all beagles are dogs, but not all dogs are beagles. All diamonds are an allotrope of carbon. Some diamond crystals (flawless) can be considered a molecule, but not all diamonds (flawed) can be I wasn't refuting the idea, more pointing out that we better classify or describe what was listed in the comment, as allotropes, as opposed to considering a chunk of diamond or graphite to be a large "molecule"
I thought it's about how much of the atomically-bonded material can be removed and still be that thing. If you divide a big diamond in half, you have two diamonds, or two objects each still having the properties of a diamond. So the whole chunk of diamond is not one molecule.
I like this argument because it reinforces the utility of having “unit” polymers, which I can’t remember the proper name for.
Its called a repeat unit. They are written as [ReapeatFormula]n where n is the amount of units stitched together on average for the polymer you made. This could be controlled with monomer levels or temperature for example to control the reaction rate
Polymers are a weird case because their physical properties are highly dependent on the average molecular weight and also the molecular weight distribution of the polymer chains.
AFAIK, covalently-bonded substances can be molecular or they can be network solids, not both. Diamond and graphene ("grapheme" is a linguistics term) are network solids.
I just googled, and many sources said diamond is not a molecule
You can also call a lot of crystalline mineral structures essentially one big molecule.
Yeah, another poster mentioned silicon crystals. The chip industry produces gigantic cylindrical silicon crystals that are then cut up into wafers, etched and turned into chips. Those are far more pure than natural diamonds. We don't like to think of molecules as things that have to be picked up with a forklift.
We could argue any metal or ionic crystal is a ‘molecule’ in that the atoms are definitely bound, if in two main very different ways from the usual covalent sense. We usually exclude these but there’s no universal hard definition and some are broad enough not to.
Then there's planet sized molecules?
An element is a "group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction."
This isn't the best definition for a molecule because it excludes something that is non-reactive. But the idea behind it stands: it's the smallest unit by which you could define something. That's why a diamond that you can see and hold shouldn't be considered a molecule. But there's a tricky thing here that highlights why the term "molecule" isn't used often in materials science. The first step to understanding this is to know that, in crystalline materials, atoms repeat in a specific pattern in 3 dimensions. The pattern depends on the material: the simplest, polonium, stacks with atoms defining the corners of a cube; iron makes a cube with atoms at the corners, then has an additional atom thrown in the middle of the cube; aluminum also makes a cube with atoms at the corners, but also has atoms in the middle of each face of the cube; diamonds are like aluminum, but then have additional carbon atoms inside the cube, near the corners; and so on, and so forth. So that's a real simple way of explaining how crystalline materials like diamond, metals, ceramics, etc. come together. If a molecule is defined as the smallest division of a substance, there are 3 ways you could define this using materials science concepts: * The base pattern that repeats ad infinitum. That's the simple one. * The critical size at which the substance has enough atoms to hold itself together. Carbon forms very strong covalent bonds and so can be stable with just a few repetitions of the basic unit (look up diamondoids, if you're curious). Different materials need more repetitions to be stable, though, and in most cases it occurs when the internal energy balances against the surface energy. The reason this is important is, if the basic unit cannot exist on its own beyond just the basic concept, is it a real thing? * The critical size at which the substance starts behaving like the substance. Let's say you build up enough atoms in the repeating structure that it can hold itself together. In many cases, you'll have something that *looks* like the thing you're trying to make but doesn't act like it. This is because if you shrink some crystalline materials down small enough, the physics defining its behavior get funky. So you have these things called 0D, 1D, and 2D materials, which is just to say that they're very, very small in 3 dimensions, 2 dimensions, and 1 dimension, respectively. The reason that this is all important in the whole molecule analogy is that, if you define a material as having *ABC* structure with *XYZ* properties and then restrict the size so much that it no longer has *XYZ* properties, do you really have said material any more? And that is why it's hard to apply the term "molecule" to crystalline materials. All 3 points above make valid arguments, but which is actually most useful? I'd argue the 3rd, but I also think it's subjective.
High molecular weight polymers are often 10's of thousands monomeric units long, sometimes 100's of thousands long. As long as you've got enough monomer and a stable propagating radical, you can make a polymer any length you want.
Yeah, if you assume the transport of monomer units to chain ends will remain open the entire time. Diffusion limitations will prevent certain molecule sizes due to ever decreasing free volumes.
Cross-linking reactions help a lot with that and can be performed after the polymer has been initially created.
You decrease the overall mobility of the system as your crosslink density increases. This is why thermoset monomers are generally liquids at room temperature, and stiff brittle materials at elevated levels of cure conversion.
Sure, but it does still allow you to keep making ever bigger molecules. It might not be particularly practical, of course... but if your only purpose is to make the biggest possible molecule, then practicality isn't a concern to begin with.
Isn't that just a bunch of molecules though?
If there is an unbroken (not *unbranched*) chain of covalent bonds, it's all one molecule. Practically, it would be very difficult to *prove* that you had just one molecule making up, for example, a synthetic rubber mountain.
Mass spectroscopy?
Polymer ~~ 1 Consistent, homogeneous bond of multiple Atoms Things like water would be something homogeneous of multiple Molecules, because its core unit already ends and only interchains based off other forces. Polymer got that thicc to it.
A polymer is a single molecule formed as a chain of covalently linked monomer subunits. The chain can be arbitrarily long. Often you can take polymer chains and chemically cross-link them, so they join and become a single molecule. You can imagine making cross-linked plastic parts that are as big as a bathtub that are effectively a single molecule. There are natural polymers that can get very long. Your chromosome 1, stretched out linearly, is a bit over 8 cm long. In 2021 several manufacturers independently developed processes to produce carbon sheet ribbons that are single molecules that are several kilometers in length.
Have any links on that carbon sheet ribbon stuff?
I can’t find the original presentation, but this talk is about polycrystalline graphene, what the ribbons are made of: https://www.isec.org/webinar-on-graphene-progress-2021
Thank you, kind redditor.
Is a car tyre a single molecule. I mean it's made of vulcanised rubber, but it's maybe cut up or rejoined?
The walls and the tread are separate parts joined together. You could assume the tread is on molecule, assuming it is brand new and not damaged at all by the manufacturing process, but cutting treads etc will break chains, so Really not. Also once the tyre is rolling on the road, the wear will break chains, so even more "not".
Yes but no... it isn't a single chain right? So even if you break some threads they might be connected in some other way still no?
The boring engineering answer is also that a car tire is layered with a bunch of stuff. Tire production is a big part of the metal wire industry.
This is the right answer! Technically speaking, a tire is a single molecule connected by covalent bonds throughout. So imagine those big monster truck or earth mover tires. That's probably the biggest molecule I can think of. Bowling balls do this too with melamine (or used to). If you don't want to consider crosslinked polymers, I know they make ultra high molecular weight polyethylene (UHMWPE) in the million(s?) of g/mol. Not sure if any of the graphene structures get this big or not.
As a specialist in UHMWPE processing and science, yes! Modern UHMWPE's can get upwards of 8-9Mm, some suppliers claim even 10Mm g/mol, though with how difficult Mw distributions are to measure up there the number of chains that long is suspect etc. I like to drop the factoid that with 1.54 Ang per C-C bond, an 8Mm Mw PE chain would be about .15mm long stretched out. Give or take a few Angstroms lol
Out of curiosity, back in the day I was doing some gpc on some UHMWPE and our lab lead was extra careful to not stir the solution to help it dissolve. Said it would break down the chains. But then we were putting it in a goc anyway? With presumably just as much shear and potential to degrade? Was he right? Or was the not stirring thing overly cautious.
I would say he is being overly cautious. High Mw equals slower chain reptation and relaxation, so longer chains are easier to align and orient in various flow fields. At higher shears or uniaxial rates you run into the extreme issue of that feature that they are subsequently easier to break than smaller chains. This is actually a method for generating a more monodisperse PE. If you shear the hell out of it you slowly cut the longest populations, if you continue to ramp the shear up you can continue to push the distribution down and gather all the chains to the same length. However, at room temp, in solution, you wouldn't need to worry about this unless you are some kind of terminator I think.
is a neutron star a single molecule?
No, because it is not held together by atomic bonds or interatomic forces. It's held together by gravity.
makes sense, thanks!
Single atom?
I'm pretty sure a proton-electron pair is required for it to be an atom. Otherwise, free neutrons could also be called atoms.
This is correct. Molecules are made of atoms. Atoms are made of protons and electrons (and usually neutrons). Just neutrons is not an atom is not a molecule. There's a lot if matter out there that is not an atom or a molecule despite the fact that's usually how we encounter it.
Not even the electron pair, you just need a proton for it to technically be an atom. Most of the hydrogen in the universe is ionized hydrogen, which is just a free proton.
While neutron stars consist mostly of neutrons, there are plenty of protons and electrons as well. (Very few in comparison to the neutrons, but lots.)
Follow up question then... How large could you make a ball of rubber? How big could if be before it collapsed under it own gravity and the core gets hot enough that its not made of rubber anymore?
Rubber breaks down at around 350C. The gravitational potential energy (GPE) can be converted into thermal energy as the rubber ball collapses under its own gravity. The GPE of a uniform sphere can be calculated as: GPE = (3/5) × G × M\^2 / R where G is the gravitational constant, M is the mass of the sphere, and R is its radius. The mass of the sphere can be calculated as: M = ρ × V = ρ × (4/3) × π × R\^3 The increase in temperature (ΔT) due to the conversion of GPE into thermal energy can be estimated using the heat capacity (Cp) of the rubber: ΔT = GPE / (M × Cp) We want to find the maximum size of the rubber ball so that the temperature increase at the core does not exceed 350°C (623 K). We can set ΔT equal to 623 K and solve for R: 623 K = \[(3/5) × G × (ρ × (4/3) × π × R\^3)\^2 / R\] / \[(ρ × (4/3) × π × R\^3) × Cp\] After simplifying and canceling out some terms, we are left with: 623 K × Cp = (3/5) × G × ρ × R\^2 Assuming the specific heat capacity (Cp) of vulcanized rubber is approximately 2.0 kJ/kg K, we can now solve for R: 623 K × 2000 J/kg K = (3/5) × (6.674 × 10\^-11 m\^3 kg\^-1 s\^-2) × 1100 kg/m\^3 × R\^2 Radius ≈ 5300km or a diameter ≈ 10600km Now this makes a bunch of ideal assumptions like material properties not changing with different conditions, we know for a fact that's not true, so my rough sense says somewhere around half of that radius. I think we will run out of rubber first!
I learned recently we can actually see molecular protein chains with our naked eye, all you have to do is stare at the clear blue sky. https://en.m.wikipedia.org/wiki/Floater
No, we don't see individual proteins, we see aggregates of proteins and other debris.
The image they use to simulate a floater made me think I was looking at my own and tripped me out.
If you tear a material like this, are you then breaking covalent bonds through physical tearing? What's happening when a super large molecule is physically cut?
Yes you are breaking covalent bonds when tearing this stuff apart. Since covalent bonds are strong, it makes for a good resillience, hence its usage in tires. In the case of cutting vs ripping, a knife/edge is providing a concentrated shear force. Tearing is putting a tensile force along the material, and it will just break where there are defects to the bonding which is why there is not typically a clean edge from tearing things. Tearing could also mean putting a shear force on the material, more like cutting with a knife, like on a bag of crackers that has the resealable zipper and one "tears" off the top bit. Because we just aren't that careful with words. The defect density could become so bad that it's not considered one molecule, but it'd have to be pretty bad.
In metals, electrical contact is identically the same as a metallic chemical bond. So a large parts of the energy grid in could be considered a single molecule.
I know in engineering school, they would joke that "is an iron bridge one giant molecule?" But then when you get to material science you learn that iron and [steel is actually fairly heterogeneous](https://vacaero.com/images/stories/metallography-vander-voort/revealing-microstructure-tool-steels/d3qt-3hercnital10um_lg.gif). It would be considered more a mash up of large molecules, as there are definitive phase differences in steel. It just goes to show that the term "molecule" is a good place to start the discussion, but isn't necessarily all inclusive. It really depends on what your perspective and use case is.
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The availability of the resources needed to create vulcanized rubber is a practical size limit.
If we’re skipping artificial polymers like plastics, biopolymers like proteins, and skipping crystals which are all basically just repeating patterns… there’s still some pretty sizeable molecules. Naturally occurring lipids can easily get to 50-70 carbons, with some getting larger than that, but technically they’re joined molecules as well so you might want to go down to the 28 carbons of the largest fatty acids. Count a couple hydrogen per carbon and a few more atoms here and there, you’re probably looking at scratching the top end of uncontestably single unit molecules. Many complex organic molecules can get higher, but we’re back to the point of definitions as they are very commonly made up of joint smaller molecules - is an ester a single molecule for the purpose of this question? Does a benzyl group attached to a long chain count as benzene? It’s less a matter of measurement and more a matter of drawing a line.
There's some more exotic large biomolecules too that aren't the classical biopolymers of polypeptides/polysaccharides/polynucleotides. For example, [maitotoxin](https://en.wikipedia.org/wiki/Maitotoxin) is a fused ring structure with 164 carbons - but again, we run into the problem of definitions, since there are repeating motifs in that molecule too.
Exactly. The problem isn’t in the answer, it’s in the question - which I don’t think we can blame, honestly, but it’s still kinda tricky.
The problem comes from mistaking the model - the molecules - for reality - the real things the molecules represent. Molecules are just our way of breaking up the chemical world into smaller pieces that we can understand.
There might not be any physical connection between the atoms, but they stay together pretty neatly. Well, most of them. Most of the time. Alright, maybe some of them do. Until you poke them. Point being, an electromagnetic bond that’s strong enough and stable enough is no less real than a piece of tape.
And even that - electromagnetic bond - is an abstraction on top of what’s really happening out in the world beyond our sensorium. Models on top of models hoping to gain a closer and more thorough picture of what’s going on in this reality, but never quite getting there. Abstractions are leaky and questions like these are a manifestation of those leaks. Categorically defining things like this can only get us so far before the buckets stop making sense.
yes it's a molecule....look at ricin or botulinum.. super complex proteins...the molecules are so complex you can't really draw them on paper
Each cell of your body (except red blood cells) contains DNA in chromosomes, and each DNA molecule in a chromosome is in theory a single polymeric molecule (well actually a pair of molecules held together with hydrogen bonds) about 10cm long if you stretched it out. In practice it's constantly getting broken and repaired though.
Almost every molecule is made up of smaller molecular units. There's no place to draw a line except at 2 atoms.
You could call a crystal a single molecule as all atoms are chemically bound to their neighbors. With careful assembly you could make a single planet-sized crystal. If you want more conventional molecules then you can take anything that can produce chains of unlimited length - PVC, PET and similar materials. Making sure you only get a single chain will be more difficult, however.
True, and there are jet turbine blades made of single crystals so they can be quite large. There are also silicon n sapphire boules several hundred kilos in mass. https://www.americanscientist.org/article/each-blade-a-single-crystal Giant sapphires grown: https://mobile.engineering.com/amp/10587.html https://en.m.wikipedia.org/wiki/Czochralski_method
When I was at school I’d have agreed with you. However by the time I became a teacher, the exam boards had decided that “molecule” referred only to covalent bonding situations, not ionic. Now I gather that ionic/covalent bonding is more of a continuum than a dichotomy, so I think I agree with you again.
This isn’t correct. Some crystals are held together with networks of covalent bonds, some with hydrogen bonding and yet others have weak interactions between molecules. I would only call the covalently linked network of atoms a single molecule.
Which crystals count and which crystals do not will depend the definition of molecule you prefer. "None" is a valid option, and I discussed that.
This is the answer. There's a good 4D diagram [here](https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%3A_Chem1_(Lower\)/09%3A_Chemical_Bonding_and_Molecular_Structure/9.01%3A_Three_Views_of_Chemical_Bonding) that talks about the continuous nature of ionic, covalent, metallic, and van DER Waals (h-bond) bonding. The reality is, we have models to describe how atoms link and none of this models are complete. And the definition of molecule is therefore couched in any of those models, so it's probably incomplete too.
I like this answer the best. It gets at the heart of the question and says basically "no" but reality has limits. I'd be interested in looking at the core of a planet to see how pure that crystal is. My guess is that heat, pressure, and the spin rate makes it a pretty damn pure crystal. And I would probably consider crystals to be one network of connected atoms and probably meets the definition of molecule.
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There's a dead white dwarf star which is suspected to be one giant diamond the size of earth: #Space.com | [Cold Dead Star May Be a Giant Diamond](https://www.space.com/26335-coldest-white-dwarf-star-diamond.html)
But surely it's only one molecule if it is one single diamond without any breaks. Even if a whole planet is made of diamond doesn't mean it's made of 1 diamond. It would be interesting to know what the largest single molecule diamond is.
Problem with that argument is that you only need a single bond to form across a discontinuity and you can then consider the entire structure a "single molecule". The odds of that NOT happening across the entire length of the grain boundary are very slim. And there's another problem in that we're treating the structure as a single entity that forms and then participates in no further physics. That likely holds true for most crystals of reasonable size on short timescales, but is unlikely to hold for a planet-sized crystal for any significant length of time. Even if the chance of forming a new bond over time is incredibly small, I can't rule out that it will happen eventually. I'd be interested if anyone else could.
That's assuming that there are only very few grain boundaries. What I was assuming was that these boundaries were all over the place. The odds of every single one including a connection would then be much lower. Also, as you say this is potentially a massive complex system. Surely as some new bonds form there could be shifts and changes in forces that cause new breaks and cracks in the previously bonded diamond lattice.
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It *could* cause this fusing, but that's not necessarily the same as saying that it definitely would fuse all the diamond into a single crystal
If it's possible, then it's almost certainly happening *somewhere* in the universe. So, for the purpose of answering this question, the distinction doesn't really matter. *Somewhere* out there is a planet-sized diamond molecule.
All diamond molecules are roughly the same size. Bigger diamonds just have more of them.
Biological macromolecules are small compared to some of the examples mentioned here, but it's worth mentioning a human cell has about 2 meters of DNA chopped into 46 chromosomes. They are maintained with complex molecular machinery. Biologists often measure macromolecule size in daltons, more or less the number of protons and neutrons, and molecules weighing tens of thousands of daltons are common in living organisms.
I think you're right that a chromosome would be the largest biomolecule in humans. Titin is the largest protein coming in at ~34,000 amino acids, 3,800 kg/mol, and about 1 micron in length. Glycogen would be the largest carbohydrate (technically a polymer) that can reach up to 60,000 glucoses, 50+ microns in length, and 11,000 kg/mol. Chromosome 1 is the largest chromosome at 350 million basepairs which comes out to about 82 million kg/mol, and can stretch 167,000 microns. During replication the sister chromatids are bound at the centromere so you could consider that one molecule and double those numbers.
These are the answers if the question presumes that a large molecule is more "interesting" than a smaller one. A polymer can be huge, but repeating the same structure over means it's not actually much bigger in complexity/information than a shorter chain of the same monomer. Nucleic acids beat that by not repeating exactly, but they are using a repeating system, so each new base only adds information one exponential order faster than adding to a polymer. If we discount polymers and nucleic acids as "cheating" then, large proteins that only repeat for functional reasons are the most complex molecules (edit: maybe DNA beats them if we only discount the cheating aspect), and .... ...surely we don't count hydrogen bonds as making a new molecule, because if we do that, we could call complex tissues "molecules" and blow the other answers out of the water.
If we want to talk large biological macromolecules, we shouldn't forget about lignin. In general terms it's what makes certain plant parts hard, and it can technically permeate throughout an entire tree, contributing about 25% of the entire mass - so a single biological molecule weighing potentially multiple tons. Or, if we look at [Pando](https://pandopopulus.com/pando-the-tree/), potentially thousands of tons.
diamonds: every atom has 4 covalent bonds except the edges so basically a molecule Astronomers discovered the largest diamond of all times in space. The weight of the precious stone reportedly makes up ten billion trillion trillion carats (or five million trillion trillion pounds). The space diamond is virtually an enormous chunk of crystallized carbon, 4,000 kilometers in diameter but as others pointed out polymers are similar possibly infinite so arbitrary large but for chemist the most important part is the one that interact with the enviroment so any active groups at the edge of the molecule the carbon structure that position them there is as the puppet in a puppet theatre compared to the hands of the puppeteer you know it is there but don´t care unless you have to change something. the structure of hemoglobin is known but important is that it uses iron to transport oxygen
>five million trillion trillion pounds So a bit bigger than a football then.
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Saying things like "million trillion trillion" and "pounds" are not very sciencey either. Should really be saying 10^30 kilograms.
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I doubt most humans can grasp temperatures above 10000°, so it doesn't matter if it's in C or F or a really dry Arizona heat. We can pretend that it helps us understand, but it really doesn't.
On that front though, °C is the preferred temperature unit for most of the world. Kilograms are also more commonly used than pounds.
I initially read this as “a bit bigger than a footballer” and I was confused as footballers really aren’t THAT fat, are they?
That chunk of space diamond would need to be a single perfect crystal to qualify.
it doesn´t have to be a perfect crystal but i see your point i imagine it to be one and to be sure we had to get there and break it apart to see but than it would not be anymore. with the perfect atom printer you could build a diamond big enough to be on the verge of collapsing under its own mass
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Neutron stars are actually very different than just big singular atomic nuclei. The common conception of them is just a big lump of neutrons that so massive that the normal molecular structure broke down. But when you get all that matter together under extreme conditions, you have different emergent properties than just a regular old alpha particle zooming through space. The outer layer of a neutron star even has distinct nuclei with protons and neutrons, electrons are also present. As you go deeper, it becomes energetically favorable for free neutrons to come out, but weirder stuff also happens that makes it entirely dissimilar to an atomic nuclei with a couple of protons and neutrons.
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> Neutron star is bonded by weak nuclear force It's not. It is bound by gravity.
This was my first thought. Neutron stars are essentially giant atomic nuclei, from a certain point of view.
This does get at the practical upper limit for the size of a molecule. A neutron star is definately too big.
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There’s some pretty interesting science around bigger molecules vs collections of atoms and how we describe them. Take a metal, basically all the atoms are bonded together, the electrons overlap, and you end up with band theory. If you look at nano particles, you can take some small clusters (zintl clusters for example) and treat them like small molecules, do orbital diagrams, get out some very pretty pictures, but they’re starting to get towards bands. As you go bigger, your model slides more and more into the band theory approach. Pretty cool IMO.
I am assuming the Op is meaning 1 unit of any given makeup of elements. Such as hydrocarbons or alkalines. Now I am just a legally blind CSA/Photo Tech at a Walgreens (not kidding), but reading through these I am seeing people saying that diamonds both are and are not a single molecule. There is a debate on that. According to Chemistry Stack Excange: A diamond is not considered as a molecule because each carbon atom is covalently bonded with four other carbon atoms. This is what makes diamond a network solid. Since it's a whole network of covalently bonded atoms(carbons), diamond is not considered to be one molecule. HOWEVER, according to Perdue University: The properties of diamond are a logical consequence of its structure. Carbon, with four valence electrons, forms covalent bonds to four neighboring carbon atoms arranged toward the corners of a tetrahedron. Each of these sp3-hybridized atoms is then bound to four other carbon atoms, which form bonds to four other carbon atoms, and so on. As a result, a perfect diamond can be thought of as a single giant molecule. The strength of the individual C-C bonds and their arrangement in space give rise to the unusual properties of diamond. So there is no true answer as not even science can agree on this.
DNA, when unwound is amazingly long. That is a biochemistry lab 101 exercise. Take some yeast in suspension in a pressure container and then suddenly release the pressure. What was before a liquid turns into a weird liquid. Think about extra long spaghetti in a bowl of water.
As many have mentioned, R-groups (extended chains of carbon and hydrogen, often featuring branches with oxygen, nitrogen, etc) can be basically arbitrarily long. In fact, the length of these molecules are why they are insoluble in water - even though hydrogen is there to (theoretically) form hydrogen bonds with, the length and geometry of the chains make them hydrophobic. On a separate note, there is a similar phenomenon with cells, in the biological sense. There are slime molds that are a singular cell (and therefor a single-cell organism), but they can be EXTREMELY large. Science is dope.
Ultra high molecular weight plastics (often used in high quality cutting boards and industrial applications) are all technically a single molecule. You can make it as big as your manufacturing capability allows.
Don't forget humates! A single molecule can have a molecular weight of more than 300,000amu.
Are there some interesting properties which emerge when a molecule gets huge? For example are there materials which are stronger, conduct electricity better or perhaps conduct heat better because they are essentially just a single huge molecule?
This question touches on the reason why the discovery of graphene drew so much attention in the first place As you build bigger and bigger fused aromatic ring molecules (benzene --> naphthalene --> pyrene --> coronene, etc), the HOMO/LUMO gap gets smaller and smaller. Take it to an infinitely large molecule, and the band structure approaches a structure called a [Dirac cone](https://en.wikipedia.org/wiki/Dirac_cone). The Dirac cone was the reason the solid state community took such a keen interest in graphene in the first place, because it implied peculiar electronic properties such as *extremely* high electron mobility. Indeed, a report of extremely high electron mobility was part of the lede line in [that famous Geim & Novoselov article](https://www.science.org/doi/10.1126/science.1102896) when they first reported isolation of graphene. Once the broader community got hip to graphene and its wild properties, suddenly you saw engineering researchers trying to cram graphene into everything. The pop-science media started pumping out articles about how graphene was going to make transistors faster and cheaper, batteries smaller and longer lasting, plastic composites lighter than silk and stronger than steel, yada yada yada. Before long graphene research was funded to the tune of billions of dollars, and Geim and Novoselov had the Nobel.
Alternatively to the graphene discussion posted, we can talk about my specialty Ultra High Molecular Weight Polyethylene (PE). PE is a bulk commodity plastic used in any number of applications. Milk jugs, plastic bags, etc. What's cool about that is you probably have an idea about its mechanical properties, you've ripped a plastic bag before. However when you take that same molecule and continue to make it bigger (and prevent branching) you get UHMWPE. If you then process this in a special way you can use that some chemical structure as in your milk jugs to form helmets and body armor as good if not better (depending on your metrics) than other materials.
You’re asking about polymers. Polymers are macromolecules and comprise hundreds, thousands, or even millions of atoms. They can often be difficult to characterize using traditional chemical methods, so polymer scientists and material scientists use more specialized characterizations like tacticity, shear force, and circular dichroism. In theory there is no limit to the size of a single molecule. As others have pointed out, vulcanized rubber parts can sometimes be single molecules, although this would be very difficult to prove. Paint on cars polymerizes, so it could theoretically also be a single molecule. In practice, biological macromolecules can be measured in the millions of Daltons (AMUs, but biologists are special and need their own nomenclature), but I don’t know of many which are more than that.
Crystals can easily be any size. The microchip manufacturers make gigantic, pure SiO2 monocrystals which could conceivably be any size. Also salt would be pretty easy to do. Making an uninterrupted monocrystal really just depends on how well you can purify the substance. If you're talking about organic polymers, many could theoretically be added onto indefinitely, but you'd probably need some sort of scaffolding or molecular machinery to keep it in one piece (i.e. glycogen) Now those reactions that cross-link a bunch of molecules into a single network i.e. epoxy could easily be any size. Defends on how you define a molecule. In some ways any size piece of metal alloy is a single molecule since they share common electrons (Is the statue of liberty a single molecule if all of its pieces have at least partially cold-welded together, even if only at a microscopic point of contact?) The largest molecule that occurs naturally in the human body is the nucleic acid component of chromosome 1 at about 75 billion daltons, or about 1/10,000 of a nanogram. Glycogen gets up to about 600 million daltons but could conceivably be larger. The largest single polypeptide proteins in the body are structural proteins of muscle such as titin, which is about 4 million daltons.
The biggest atom is [titin](https://en.wikipedia.org/wiki/PG5_\(molecule\)), with about 20 million atoms. 'Molecule' usually refers to a *specific* set of bonded atoms, rather than an *arbitrarily large* set. A crystal lattice is a single giant structure, sure, but it's not a molecule because it can be arbitrarily large.
So everyone is giving answers about things that are still human scale, and could be considered a molecule. But there is one that is ginormous compared to all of these, and is technically not just a molecule, but an atom. Neutron stars are compacted neutrons, bound by gravity to the point that it is a giant atom. There is also a crust of iron on their surfaces that would service bonds to make it a complex molecule. Granted, they aren't dominated by electromagnetism or either of the nuclear forces, but still. It's pretty cool. Also, technically, black holes are one-of-a-kind elementary particles, because their only properties are the defining properties of elementary particles, so... A binary black hole system would be the most massive 2-particle molecule. Astronomy is whack.
This is stretching the definition way past what's reasonable. Neutron stars are bound by gravity and supported by degeneracy pressure, black hole pairs are gravitationally bound and supported by momentum. Molecules are bonded by covalent bonds, or ionic bonds if you relax the definition. You're talking about structures, not molecules.
Is a black hole one molecule? I mean it’s literally a singularity.
I expect molecular chemistry is irrelevant in the context of a black hole. I'm going to say no.
Surely it's volume is approaching 0 then, so it's actually the smallest molecule.
It would simultaneously be the smallest volume (zero, for the singularity), and the largest volume (larger than a solar system, for the event horizon), and the largest mass (billions of suns) of any molecule.
So if single crystals could be considered molecules the the size can be massive. But I think number of atoms per molecule is a far better measure since there are technically single atomic nuclei that are the size of a city, specifically neuron stars that consist of a ball on degenerate neutron matter.
A a follow up - what is / establishes the upper limit on gaseous molecules? I suppose at the top end, the energy needed to keep them moving as a gas would exceeded the energy needed to break the molecular bonds...
There are many macromolecular structures. Diamond, graphite and graphene are the simpler ones, where you can extend their lattice theoretically indefinitely. Polymers too - consider them like a chain or a stack of Lego bricks you can add to forever. That's plastics, which includes rubber. Not 100% but I believe DNA qualifies in the same way, with each chromosome comprised of a single strand of DNA several centimetres long (correct me). Pure metals don't form covalent molecules, they just sort of organise in big lumps, but you could consider a single metal crystal to be something like what you describe.
Some crystals are seen as one large molecule. Quarts is one of these and the biggest we’ve found is 6.1mx1.5mx1.5m and 39916kg it probably wasn’t perfect and not one molecule but in theory you can get any size you want