6 ms·

The explanation, as described in the article, is lacking, since it does not really explain why no other elements are liquid. The suggestion is that it is that

by evanb 13y ago

The explanation, as described in the article, is lacking, since it does not really explain why no other elements are liquid. The suggestion is that it is that the 6s orbital is full. Why don't other large-Z elements with filled p- or d- or f- orbitals also become liquids?

VLM 13y ago
TLDR is they do. The medium form answer is look at the periodic table. There's block of s (which don't count because other than H/He they are buried deep in the atom) and a block of d where the full ones do have ridiculous low melting points compared to neighbors (like Zinc, Cadmium, Mercury...) and a block of p shell where the full p shells are the well known noble gases which are liquid at really low temps and the block of f weirdos who don't matter. As for the f weirdos not mattering look at the electron configuration for something like Tb. Yes very nice that it has a peculiar collection of 4 level f shaped orbital electrons but I guess the more influential effect is the 5 level s and 5 level p and more importantly the 6 level s way out there in front of the mere 4 level f. Its kind of like D+D or pathfinder multiclass, oh, you have 2 levels of bard multiclassed into your level 10 sorcerer, well whatever, that bard isn't going to matter very much compared to the sorcerer level powers. So back to your question, the filled p make great gasses at room temp not mere liquids you are totally correct here, the filled d have really low melting points for metals like Hg being a liquid as discussed, and the filled f are weirdos who fool around with electron configurations at mere level 4 when the real chemical action is at level 6 so they don't matter (sorta) For a more correct, longer form answer someone else will have to step in.
- davvolun 13y ago
  Favorite analogy ever. Don't really know why the 4 level f shaped orbital electrons are a level 2 multiclassed bard and the two 5 level s/p and 6 level s are like a level 10 sorcerer, but that may be because I understand about 5 of the words at the beginning of this sentence. It's been a really long time since chemistry.
  - jjoonathan 13y ago
    It has to do with the principal atomic number of those f orbitals. Some quick review (where ~ means "is related to in a monotonic, increasing fashion") n = Principle Atomic Number ~ energy,size of orbital l = Total Angular Momentum Number ~ abs(ang m.)^2 n is 1,2,3,... l is 0,1,2,... (0=S 1=P 2=D 3=F ...) Now you can tell that these two should be related by thinking about the classical "solar system" electron/nucleus model: if an electron has lots of angular momentum that means it must have lots of energy. Careful: if it has no angular momentum it could still have lots of energy if it's going straight at or away from the the nucleus (angular momentum cares about velocity perpendicular to the line between two objects; energy cares about the absolute velocity). This idea turns into an inequality we get by solving the Schrodinger equation for a H atom to find eigenstates which we parameterize on the quantum numbers: l < n also we can figure out from the H-atom Schrodinger equation Increasing n only (going down a column) increases energy The different "blocks" of the periodic table are named after the l quantum number because it is instrumental in determining the shape (as opposed to size) of the orbital. S is the 2 cols on the left, D is 10 cols in the middle, P is 6 on the right, and F is down below (it should actually be between S and D blocks but that wastes space on posters). What does the inequality (and the intuition behind the inequality) tell us about these blocks? Let's go one by one S block. l=0. 0<n. n>=1. S orbitals have "size 1" or larger P block. l=1. 1<n. n>=2. P orbitals have "size 2" or larger D block. l=2. 2<n. n>=3. D orbitals have "size 3" or larger F block. l=3. 3<n. n>=4. F orbitals have "size 4" or larger This sort of looks like larger l means larger orbitals, but not so fast! They fill in order of energy level, not momentum (low energy = tightly bound to nucleus, deep in its electrostatic well). If we fill orbitals one by one, we know the first P orbital will have size 1 but that doesn't tell us anything about the S orbitals that come before it, and indeed there is an S orbital of size 2 that comes before the first P orbital of size 1. Just read off the periodic table in order of increasing (proton count = electron count) to see what I mean. OK, now we jump to the F block. We know the first f orbital we see has size 4 -- it is the outermost orbital of Lanthanum. But what is the preceding orbital, the one with slightly less energy (slightly more tightly bound to the nucleus)? It's the outermost orbital of Barium, and it's an S orbital of size 6. S orbital of size 6 is bigger than a P orbital of size 4 :-) This is counterintuitive because it breaks the "bigger orbitals have more energy / are less tightly bound" rule. The solution to the paradox is that the part of the orbital (probability density function) that contributes most to the energy is the part near the nucleus where the electron is far down the rabbit hole, so to speak. While the outermost part of 4f is smaller than that of 6s, the inner part of the 4f has pulled away from the nucleus while the 6s still sits squarely on top of it. 6s gets out to play with other atoms more than 4f but in terms of energy it more than balances that out by spending time really close to the nucleus. Hope this helps! EDIT: fixed an off by one bug on the inequalities
cshimmin 13y ago
Firstly, I'll offer that the article doesn't claim to explain why other elements aren't liquid, and simply observe that it does explain why mercury is: the math works out. But interestingly there is one other element which is liquid at STP: Bromine. Every element has a melting point, and some element has to have the lowest[1]. If Earth was just a few dozen degrees cooler, we'd have no liquid elements at "STP", a few dozen degrees warmer, and we'd have several liquid elements. So there's nothing particularly special about mercury being the only liquid metal. Check out this periodic table[2] annotated with melting temperatures. See a pattern? You might argue that the other elements in mercury's column have significantly lower melting points than the metals to the left; indeed Zinc and Cadmium have filled s orbitals as well. But putting general pattern-ology aside, the macroscopic properties of an atom are essentially completely defined by the orbital structure. Observable properties such as melting point depend on these details in a highly nontrivial way. [1] Actually many elements are gaseous at STP and have very low "melting" points. Most would actually sublimate at standard pressure. [2] http://www.emsb.qc.ca/laurenhill/science/trends2/melting%20points.jpg http://www.emsb.qc.ca/laurenhill/science/trends2/melting%20p...
- davvolun 13y ago
  It does seem unusual that there is exactly one metal that is liquid at STP (room temperature? been a long time since chemistry). On the other hand, it's always blown my mind, just a little, that the moon's orbital period and rotational period almost exactly match, so it's not like the universe isn't filled with these weird coincidences, based on relatively simple interactions exploded on macro scales.
  - vacri 13y ago
    STP is specifically 20 deg Celsius. It's in the room temperature range, but is more precise than that.
    - jacquesm 13y ago
      It's actually 'standard temperature and pressure'.
quasque 13y ago
Another metal that melts slightly above room temperature - and is liquid at human body temperature - is gallium. You can get a solid piece of gallium, put it in your hand, and watch it slowly melt [1]. Pretty neat. [1] http://www.youtube.com/watch?v=QYioZFOhxow http://www.youtube.com/watch?v=QYioZFOhxow

by evanb 13y ago

VLM 13y ago

TLDR is they do. The medium form answer is look at the periodic table. There's block of s (which don't count because other than H/He they are buried deep in the atom) and a block of d where the full ones do have ridiculous low melting points compared to neighbors (like Zinc, Cadmium, Mercury...) and a block of p shell where the full p shells are the well known noble gases which are liquid at really low temps and the block of f weirdos who don't matter. As for the f weirdos not mattering look at the electron configuration for something like Tb. Yes very nice that it has a peculiar collection of 4 level f shaped orbital electrons but I guess the more influential effect is the 5 level s and 5 level p and more importantly the 6 level s way out there in front of the mere 4 level f. Its kind of like D+D or pathfinder multiclass, oh, you have 2 levels of bard multiclassed into your level 10 sorcerer, well whatever, that bard isn't going to matter very much compared to the sorcerer level powers. So back to your question, the filled p make great gasses at room temp not mere liquids you are totally correct here, the filled d have really low melting points for metals like Hg being a liquid as discussed, and the filled f are weirdos who fool around with electron configurations at mere level 4 when the real chemical action is at level 6 so they don't matter (sorta) For a more correct, longer form answer someone else will have to step in.

davvolun 13y ago
Favorite analogy ever. Don't really know why the 4 level f shaped orbital electrons are a level 2 multiclassed bard and the two 5 level s/p and 6 level s are like a level 10 sorcerer, but that may be because I understand about 5 of the words at the beginning of this sentence. It's been a really long time since chemistry.
- jjoonathan 13y ago
  It has to do with the principal atomic number of those f orbitals. Some quick review (where ~ means "is related to in a monotonic, increasing fashion") n = Principle Atomic Number ~ energy,size of orbital l = Total Angular Momentum Number ~ abs(ang m.)^2 n is 1,2,3,... l is 0,1,2,... (0=S 1=P 2=D 3=F ...) Now you can tell that these two should be related by thinking about the classical "solar system" electron/nucleus model: if an electron has lots of angular momentum that means it must have lots of energy. Careful: if it has no angular momentum it could still have lots of energy if it's going straight at or away from the the nucleus (angular momentum cares about velocity perpendicular to the line between two objects; energy cares about the absolute velocity). This idea turns into an inequality we get by solving the Schrodinger equation for a H atom to find eigenstates which we parameterize on the quantum numbers: l < n also we can figure out from the H-atom Schrodinger equation Increasing n only (going down a column) increases energy The different "blocks" of the periodic table are named after the l quantum number because it is instrumental in determining the shape (as opposed to size) of the orbital. S is the 2 cols on the left, D is 10 cols in the middle, P is 6 on the right, and F is down below (it should actually be between S and D blocks but that wastes space on posters). What does the inequality (and the intuition behind the inequality) tell us about these blocks? Let's go one by one S block. l=0. 0<n. n>=1. S orbitals have "size 1" or larger P block. l=1. 1<n. n>=2. P orbitals have "size 2" or larger D block. l=2. 2<n. n>=3. D orbitals have "size 3" or larger F block. l=3. 3<n. n>=4. F orbitals have "size 4" or larger This sort of looks like larger l means larger orbitals, but not so fast! They fill in order of energy level, not momentum (low energy = tightly bound to nucleus, deep in its electrostatic well). If we fill orbitals one by one, we know the first P orbital will have size 1 but that doesn't tell us anything about the S orbitals that come before it, and indeed there is an S orbital of size 2 that comes before the first P orbital of size 1. Just read off the periodic table in order of increasing (proton count = electron count) to see what I mean. OK, now we jump to the F block. We know the first f orbital we see has size 4 -- it is the outermost orbital of Lanthanum. But what is the preceding orbital, the one with slightly less energy (slightly more tightly bound to the nucleus)? It's the outermost orbital of Barium, and it's an S orbital of size 6. S orbital of size 6 is bigger than a P orbital of size 4 :-) This is counterintuitive because it breaks the "bigger orbitals have more energy / are less tightly bound" rule. The solution to the paradox is that the part of the orbital (probability density function) that contributes most to the energy is the part near the nucleus where the electron is far down the rabbit hole, so to speak. While the outermost part of 4f is smaller than that of 6s, the inner part of the 4f has pulled away from the nucleus while the 6s still sits squarely on top of it. 6s gets out to play with other atoms more than 4f but in terms of energy it more than balances that out by spending time really close to the nucleus. Hope this helps! EDIT: fixed an off by one bug on the inequalities

cshimmin 13y ago

Firstly, I'll offer that the article doesn't claim to explain why other elements aren't liquid, and simply observe that it does explain why mercury is: the math works out. But interestingly there is one other element which is liquid at STP: Bromine. Every element has a melting point, and some element has to have the lowest[1]. If Earth was just a few dozen degrees cooler, we'd have no liquid elements at "STP", a few dozen degrees warmer, and we'd have several liquid elements. So there's nothing particularly special about mercury being the only liquid metal. Check out this periodic table[2] annotated with melting temperatures. See a pattern? You might argue that the other elements in mercury's column have significantly lower melting points than the metals to the left; indeed Zinc and Cadmium have filled s orbitals as well. But putting general pattern-ology aside, the macroscopic properties of an atom are essentially completely defined by the orbital structure. Observable properties such as melting point depend on these details in a highly nontrivial way. [1] Actually many elements are gaseous at STP and have very low "melting" points. Most would actually sublimate at standard pressure. [2] http://www.emsb.qc.ca/laurenhill/science/trends2/melting%20points.jpg http://www.emsb.qc.ca/laurenhill/science/trends2/melting%20p...

davvolun 13y ago
It does seem unusual that there is exactly one metal that is liquid at STP (room temperature? been a long time since chemistry). On the other hand, it's always blown my mind, just a little, that the moon's orbital period and rotational period almost exactly match, so it's not like the universe isn't filled with these weird coincidences, based on relatively simple interactions exploded on macro scales.
- vacri 13y ago
  STP is specifically 20 deg Celsius. It's in the room temperature range, but is more precise than that.
  - jacquesm 13y ago
    It's actually 'standard temperature and pressure'.

quasque 13y ago

Another metal that melts slightly above room temperature - and is liquid at human body temperature - is gallium. You can get a solid piece of gallium, put it in your hand, and watch it slowly melt [1]. Pretty neat. [1] http://www.youtube.com/watch?v=QYioZFOhxow http://www.youtube.com/watch?v=QYioZFOhxow