4 ms·
> The increased nuclear mass causes orbiting electrons to speed up to a significant fraction of the speed of light, where the rules of Einstein’s theory of rela
by gcanyon 3mo ago
> The increased nuclear mass causes orbiting electrons to speed up to a significant fraction of the speed of light, where the rules of Einstein’s theory of relativity are important.
Fun fact: this is why mercury is liquid at room temperature. Its inner electrons move at close to 60% the speed of light, pulling in its outer electrons more tightly, making it harder for it to bond and be solid. (I am not a physicist, don't rely on my statements for your space ship design)
- sigmoid10 3mo agoI guess the more interesting question is why this doesn't happen for neighbouring elements in the periodic table?
- Laforet 3mo agoRelativistic effects are observed with many other 6th and 7th period elements. For example, the yellow colour of gold and caesium comes from altered electron energy levels due to relativistic orbital contraction, so are the special catalytic and bonding properties of platinum. https://en.wikipedia.org/wiki/Relativistic_quantum_chemistry https://en.wikipedia.org/wiki/Relativistic_quantum_chemistry
- gweinberg 3mo agoOP claimed relativistic effects explain why mercury is liquid at room temperature. That may be part of the story, but it isn't the whole thing, since other heavy elements are not liquid at room temperature.
- nyrikki 3mo agoExplaining relativistic effects in plain text forums to a general audience is a big ask, but here is a link to the first study[0] that gave evidence but it has long expected. [0] https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.201302742 https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.201302...
- sigmoid10 3mo agoThat still doesn't answer why these relativistic effects don't cause neighbouring elements to be liquid. Electron velocities should be quite similar for them. There must be something apart from relativistic effects that makes mercury special in that regard.
- nyrikki 3mo agoGold is right next door, relativistic effects shrink both Gold and Mercury’s 6s orbitals. In gold it changes the color, in Mercury it changes freezing temperature. Gallium has a low melting point 29.76C but that is due to unique chemical bonding. "relativistic contraction" (shrinking of s and p orbitals) and "relativistic expansion" (destabilization of d and f orbitals) causes many observed phenomena. Relativistic contraction of the 6s orbital and expansion of the 5d orbital lower the energy required to excite electrons. Consequently, gold absorbs blue light. Strong relativistic contraction of the outer 6s electrons leaves them tightly bound and unavailable for metallic bonding. This results in incredibly weak atomic interactions, thus mercury a liquid at room temperature. Lead also has 6s, which is what makes lead acid batteries work as well as they do. So while the observed effects change, there are relativity effects with several nearby neighbors.
- sigmoid10 3mo agoI think you still misunderstood the question. Noone asked if there are relativistic effects with neighbors. In fact, it was said at the very beginning that they certainly have these relativistic effects too. The actual question is why are gold/thallium/cadmium etc. not liquid. There must be something apart from relativistic effects that explains why mercury turns into liquid at room temperature and these others don't.
- tikej 3mo agoI think a relatively simple explanation is that on one hand mercury is liquid due to its closed-shell (a bit "noble-gas-like") electron configuration: [Xe] 4f14 5d10 6s2 and that it since its electrons are paired it makes it less energetically favorable to create strong bonds. So consequently Hg does not form conventional, strong covalent bonds (although it probably does form some weak van der Waals complex) like, for example, gold (with the unpaired electron on 6s orbital so [Xe] 4f14 5d10 6s1 configuration) and other "horizontally neighboring" elements which consequently create stronger bonds. However, this alone is not enough and would not explain why Cd isn't liquid. And here come the relativistic effects, which essentially scale with nuclear charge of the nucleus come to play and they are significantly stronger for Hg than Cd. If I remember correctly (although I read about it a long time ago so I may be a bit rusty) these strong relativistic effects cause something called "relativistic contraction of the 6s orbital" which results in the electrons on this orbital being more strongly bound than they would be, if there would be no relativistic effects (which can be theoretically compared by setting c -> infinity in the equations used to solve electronic structure theory). AFAIR Copernicium should also be liquid in room temperature for similar reasons, but since it is not very long lived and it is difficult to produce testing this will likely be very hard if not impossible to check (though if I remember correctly there was something called "relativistic maximum" which happens in the 6th and not 7th row of periodic table for some reason, so it should be higher than for mercury; though I can't remember the details why this is so). Of course this is a bit simplified picture and there are surely more details regarding how exactly relativistic effects influence the energies and consequently how this influences the melting temperature of mercury (I suppose they are in the Calvo, Pahl, Wormit and Schwerdtfeger paper linked earlier in this thread), but I think the combination of the electron configuration and strong relativistic effects explain why other neighbors are not liquid.
- beacon294 3mo agoIt would be the element underneath it which is synthetic. But it is interesting that all the elements in that row are soft or brittle in pre form or in some compounds.
- gus_massa 3mo agoIt also has an effect, it is a small correction in the energies and bounding. Sometimes it's enough to change the color or state, sometimes it's a correction like making it 1% softer or harder and is not interesting unless you are a specialist.
- LorenPechtel 3mo agoYou can start your car. Without relativistic effects a lead acid battery would put out about .2V rather than 2V.
- zyklu5 3mo agoNice! Thanks for this. More details at: https://arxiv.org/abs/1008.4872 https://arxiv.org/abs/1008.4872
- lr1970 3mo agoThanks for the link to the paper published in 2010 (16 years) ago. The OP article from Brown reads as if they were the first to establish importance of Special Relativity for heavy atoms which is not true.
- LoveMortuus 3mo agoI feel like that's often the case, right? Even gravity being describe first by Brahmagupta and Bhaskara II before Issac.
- amelius 3mo agoMeanwhile there are quarks inside every regular atom moving at speeds like 0.99995c ...
- gcanyon 3mo agoInteresting -- does that have any macroscopic/real world impact?
- moelf 3mo agowell, 90%+ of the mass of a proton comes from moving stuff, rather than rest mass of the quarks. so the real world impact is, having anything at all
- amelius 3mo agoAnd this mass is again an emergent property of Einstein's relativity ...
- prox 3mo agoI think I recently learned that the Higgs is actually not that much part of imparting mass for atomic particles. I thought it imparted all mass.
- ChrisClark 3mo agojust enough to keep electrons from staying at light speed like photons
- mr_toad 3mo ago> I thought it imparted all mass. It’s all relative; in the quarks frame of reference it does get all its mass from the interaction with the Higgs field.
- prox 3mo agoI really want to read more about this. It’s fascinating but also very difficult to wrap your head around. I did enjoy the Feynman talks.
- gigatexal 3mo agoThis is the coolest fact I’ve learned in a long time. Thank you!
- sehugg 3mo agoAnd relativity describes the orbit of the quick-moving planet Mercury which shares its name with the quick-flowing element. What a world.