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has anybody ever noticed the relationship between boiling/ melting etc..
and the atomic weight of an atom. that roughly the higher the atomic mass the higher the boilig point.
good this be a penguin effect where the more nnuetrons and protons there are the higher the melting point is.
Few elements exist for long as lone atoms and form into molecules (even if its a "pure" combination, like C4 or H2). Only the Noble Gases just sit there. As a result, boiling/freezing points end up having more to do with the *configuration* of the *molecules* that get formed, than the underlying atomic weights. Although you will see correlations, there are probably more exceptions...
Plays a Chemist on Hypography,
Buffy
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well without the few exceptions the general trend happens because of electrostatic forces between the atoms - the bigger they are the more charge they carry and the better they can 'hold' onto the other atoms nearby. This means more energy (heat) is needed to break the bolds and either melt or boil it.
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Hmmm, it isn't really so simple, the forces aren't proportional to Z, and Buffy many atoms including the metals don't form *molecules*. Even NaCl fr'instance isn't really a molecule.
Quote:
Originally Posted by anglepose
roughly the higher the atomic mass the higher the boilig point.
I don't think iron (Z=26) melts more easily than copper (Z=29) or zinc (Z=30), even less compared with tin (Z=50) lead (Z=82). What about... mercury? (Z=80)
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Hmmm, it isn't really so simple, the forces aren't proportional to Z, and Buffy many atoms including the metals don't form *molecules*. Even NaCl fr'instance isn't really a molecule.
Yah, that's what I meant. Man, NaCl and other lattices do all sortsa weird things. Do you know what the melting point of a Buckyball is? The point is even if you limit yourself to molecules, you're going to have more exceptions than rules to the gross correllation that is sorta-kinda there, so what we're all saying angelpose, is that your proposition is really not true, nor is it tremendously valuable....its kinda like saying "lots of plants are green": its sorta true, but there are so many exceptions that its not really a useful statement.
Is it getting hot in here?
Buffy
__________________ "If you do not agree with anything I say, I'll not only retract it, but deny under oath that I ever said it!" __________________________________________________ ______________-- Tom Lehrer
"What, you guys couldn’t even wear one of your tuxedo t-shirts? I mean, I know each one of you have one."
Well, simplification was the goal, I kinda assumed if I phrased the sentance "Few elements exist for long as lone atoms and form into molecules or lattices or tubes or ..." that I would have lost the introductory-level audience... Over-simplification has its place...
Pedagogically,
Buffy
__________________ "If you do not agree with anything I say, I'll not only retract it, but deny under oath that I ever said it!" __________________________________________________ ______________-- Tom Lehrer
"What, you guys couldn’t even wear one of your tuxedo t-shirts? I mean, I know each one of you have one."
Sleep? What's that?
Well, simplification was the goal, I kinda assumed if I phrased the sentance "Few elements exist for long as lone atoms and form into molecules or lattices or tubes or ..." that I would have lost the introductory-level audience... Over-simplification has its place...
Pedagogically,
Buffy
And the "introductory-level audience... " thanks you
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Re: atoms and heat 
The point is even if you limit yourself to molecules, you're going to have more exceptions than rules to the gross correllation that is sorta-kinda there, so what we're all saying angelpose, is that your proposition is really not true, nor is it tremendously valuable....its kinda like saying "lots of plants are green": its sorta true, but there are so many exceptions that its not really a useful statement.
Re: atoms and heat 
