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Van der Waals forces

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Van der Waals forces

Postby Aerlinn » Wed Feb 08, 2006 10:02 am

Can anyone tell me what they are? :)
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Postby victor » Wed Feb 08, 2006 10:35 am

it's an intermolecular force created by some electronegative and electropositive atoms..
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Postby Aerlinn » Wed Feb 08, 2006 11:00 am

Ok... can you explain that more?
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Postby victor » Wed Feb 08, 2006 11:09 am

what can I explain more than that?? Van Der waals is an intermolecular force..that's all...or maybe anyone wanna help??
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Postby Aerlinn » Wed Feb 08, 2006 11:23 am

So... are the electronegative and electropositive atoms attracted to each other in this? And what do you mean by 'some'?
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Postby victor » Wed Feb 08, 2006 11:28 am

Um, aome atoms have excesses electrons and some of them also loss some electrons...after that, they began to get attracted each other.
in common language, some are nucleophylics and some are electrophylics..
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Postby baikuza » Thu Feb 09, 2006 3:35 am

van der waals forces is caused by the fluctuation on the shell of atoms in molecules.
you know, for example between H and Cl. Cl is more elektronegative so that electron can be found more in the Cl atom's side.

then this makes H has fewer electron in it's shell. quiet clear?
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Postby Aerlinn » Thu Feb 09, 2006 9:37 am

Do you mean Cl, being electronegative wants an electron and H gives it one? I'm confused. It sounds like ionic bonding...
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Postby victor » Thu Feb 09, 2006 11:33 am

Arrgh..what Baikuza said was tye tendency of drawed electron in intramolecular covalent bonding..it's truly different from VDW force..
let me explain it with ZBS then:
Imagine there are two molecule of acetic acid(CH3COOH)....if we write the simple structural formula it would be R-COOH. Um, you can see that O atom which is bound with only one binding chain have the remaining of valence electron.
Because of those excesses valence electron, some H atom from another acetic acid molecule can be drawed closer one another and forms O---H (remember, this is only a weak binding).

PS: you have to differ between intramolecular and intermolecular forces. Try to understand both of them.

Clear now?? I hope so..:wink:
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Postby baikuza » Fri Feb 10, 2006 1:35 am

then because of the electron moves not at a perfect circle.... i mean the moves look like the wave that is move at quite constant interval... you can imagine it as angle at the end of evangelion manga volume 9...(+.+)
even this forces happen on the non-polar molecules... they have a little forces to other molecules/atom(s).....this can attach other molecules/atom(s). the forces multiply by 10to minus17 of the distance between the related molecules...
okay.. i gave a wrong example.. the right is CCl4, Cl2,... etc.
... sorry.. i do not include this at my post above...
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Postby victor » Fri Feb 10, 2006 10:23 am

Naah, the definition and example that you gave were for INTRAMOLECULAR FORCE but what Aerlinn ask was the definition of Van Der Waals Forces or in other words..INTERMOLECULAR FORCES...
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Postby Aerlinn » Sat Feb 11, 2006 12:06 pm

I think I get you... So it's similar to the hydrogen bonds between molecules, the Van der Waals forces? It's a weak bond, as in, the molecules are attracted to each other?

And... what's the difference between intramolecular and intermolecular forces? :?
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