I Nature of matter: state question

[Ferrum]

im curious as this question came up in a chemistry forum and it's more of a physics question I believe .

State changes between elements of near similar number , what constitutes the extreme phase changes ?

It was answered that there is no real answer for why the phase differences occurs at all. Well it was bluntly stated that it didn't have an answer . I'm curious how true this is ? Or if it is a phenomenon of lack of current understanding ?

Thank you anyone for taking time to answer this

 

[DrClaude]

I sorry, but I don't understand the question. What do you mean by "elements of near similar number?". And what do you call an "extreme" phase change?

Maybe you could give an example of what you are contemplating.

 

[Ferrum]

Yes , I was vague . The gas element nitrogen is diatomic beside a solid state carbon on the periodic table, they are neighbors , but their phases are different , why ? Their atomic mass is similar but this phase change , at least in lighter elements seems to shift between solid and gas without any reason ? The chemistry forums stated , against my dismay, that there was not and didn't need an answer for this it "just was ", I find this disturbing .

I assumed a quantum mechanical explanation for the phase changes was most likely the reason , but I'm an undergrad and still learning . I have not found sound peer to peer literature that breaks down why this is that I can understand at my level. It's not a homework question it's a general interest .

 

[ZapperZ]

Yes , I was vague . The gas element nitrogen is diatomic beside a solid state carbon on the periodic table, they are neighbors , but their phases are different , why ? Their atomic mass is similar but this phase change , at least in lighter elements seems to shift between solid and gas without any reason ? The chemistry forums stated , against my dismay, that there was not and didn't need an answer for this it "just was ", I find this disturbing .

I assumed a quantum mechanical explanation for the phase changes was most likely the reason , but I'm an undergrad and still learning . I have not found sound peer to peer literature that breaks down why this is that I can understand at my level. It's not a homework question it's a general interest .

But that's not the ONLY difference between. You look at Xe being an inert gas, and you add one more atomic number, and you get Cs, one of the most reactive substance around (pure Cs in liquid form will combust spontaneously in air!).

The problem here is that it isn't JUST the addition of one more atomic number. You need to look at the atomic energy levels and orbitals. There is a reason why He, Ne, Ar, Xr, etc. are inert, while H, Li, Na, K, etc.. can be highly reactive. Atoms with just 1 electron in the valence shell behaves differently than atoms with 2 electrons in the valence shell, or full number of electrons in the valence shell. This also plays a part in whether they form molecular bonds, or will tend to form a solid lattice.

BTW, the phase issue isn't that crucial, because I also also get solid N at a low enough temperature or high enough pressure. So under such conditions, both C and N are solids.

Zz.

 

[Ferrum]

I see it a little clearer now , thank you, I also was wondering about this at standard pressure and temp. I can visualize a lot of the change being product of orbital configuration and lattice structure as well , but I was wondering why this wasn't brought to light at the other forum . It seemed to be an energy level matter.

I understand the bonding a little . So while carbon and nitrogen are not complete as are not hydrogen and lithium . Helium , complete shell and it's a gas and add 1 to each partlical and you have a solid lithium, why? Energy? It's it pi or sigma bonding based ? At standard pressure and temps , why?

It seemed like a orbital energy level answer to me too , I'm wondering why the responder just dodged the answer i guess , there seems to be an answer for the phase differences . Queer to me

 

[DrClaude]

There is no simple answer to your question, but it does boil down to bonding. Atoms that don't bond to others (noble gases) or only bond in pairs (like H, N, and O), will be found in the gas phase. Elements where one atom can easily bond to more than one other atom of the same kind, like C, Li, Na, etc., will form a solid.

 

[mfb]

or only bond in pairs (like H, N, and O), will be found in the gas phase.

Unless they are heavy, like iodine.

 

[Ferrum]

Ok thank you, these were assumptions I'd had , I appreciate the replies very much