3 ms·

You're right that the article doesn't mention it explicitly, but it seems to me that the explanation is "large Z and filled 6s orbital yields a liquid at STP if

by evanb 13y ago

You're right that the article doesn't mention it explicitly, but it seems to me that the explanation is "large Z and filled 6s orbital yields a liquid at STP if you account for relativity". So I wanted to know why "large Z and filled 6p orbital yields a liquid at STP if you account for relativity" is false. I think the true explanation is the one you give: STP is totally arbitrary and it's a coincidence that this is the standard we use. That is, my question was a silly one; I didn't notice that this is a coincidence. However, I think there's a related, more well-formed question: Br, Hg, and Ga are liquids (or nearly so) at reasonable Earth temperatures (from your [2], Cs is also), but all other elements seem to be solid or gas at reasonable Earth temperatures at 1 atm. Why is the range where you get a liquid so narrow? Why do melting temperatures vary so widely? What sets the scale, and how does it vary over 4 decades (or three decades, excluding H and He---I understand that quantum effects are dominant there at standard pressure)? EDIT: Would copernicium be a liquid, if its nucleus lived long enough?

cshimmin2 13y ago
Well, my point is that the macroscopic properties of an atom are the result of a quite complicated dependency on the orbital configuration. It's not like the orbitals are legos which you just clunk together to form the atom -- "stick in 4s^2 and you get conductivity, and throw in a 2p^5 for that nice deep red color". The detailed set of rules that give these results is called quantum mechanics. We have a pretty good idea of the general equation to describe an atomic system (although it's still just an approximation), but we actually don't have closed-form mathematical solutions for many-body systems. The best we can do (except for case of hydrogen, and maybe helium) is to make a numerical simulation, which is what the authors in the article did. You see, if you throw in even one different electronic orbit, you're liable to radically change the results. If the ingredients are complicated (hundreds of relativistic+quantum-mechanical particles), you're going to get complicated results! By way of analogy, consider how genes encode lifeforms: flip a few CGAT bits and you get cancer; flip some other bits and maybe you'd get some disease resistance. As to your point about the range of variation -- this is perhaps one of my favorite reasons to study physics! To paraphrase JD Jackson, "Coulomb's law is experimentally known to hold for over 25 orders of magnitude in length scale!" But consider this; the masses involved in the periodic table cover two decades; does this perturb you? The wavelengths of light emitted by a star cover many of orders of magnitude; is that a problem? (posting as alt because I left noprocrast on)

by evanb 13y ago

cshimmin2 13y ago

Well, my point is that the macroscopic properties of an atom are the result of a quite complicated dependency on the orbital configuration. It's not like the orbitals are legos which you just clunk together to form the atom -- "stick in 4s^2 and you get conductivity, and throw in a 2p^5 for that nice deep red color". The detailed set of rules that give these results is called quantum mechanics. We have a pretty good idea of the general equation to describe an atomic system (although it's still just an approximation), but we actually don't have closed-form mathematical solutions for many-body systems. The best we can do (except for case of hydrogen, and maybe helium) is to make a numerical simulation, which is what the authors in the article did. You see, if you throw in even one different electronic orbit, you're liable to radically change the results. If the ingredients are complicated (hundreds of relativistic+quantum-mechanical particles), you're going to get complicated results! By way of analogy, consider how genes encode lifeforms: flip a few CGAT bits and you get cancer; flip some other bits and maybe you'd get some disease resistance. As to your point about the range of variation -- this is perhaps one of my favorite reasons to study physics! To paraphrase JD Jackson, "Coulomb's law is experimentally known to hold for over 25 orders of magnitude in length scale!" But consider this; the masses involved in the periodic table cover two decades; does this perturb you? The wavelengths of light emitted by a star cover many of orders of magnitude; is that a problem? (posting as alt because I left noprocrast on)