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Help deciphering a definition...

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ryan93
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26 Jun 2011, 1:03 pm

I'm writing an argument about a particular branch of pseudo-science, and I need to understand the IUPAC definition of a molecule. Unfortunately, I know nothing about Quantum Chemistry...

Quote:
Molecule
An electrically neutral entity consisting of more than one atom (). Rigorously, a molecule, in which must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state.


Does this imply that there needs to be covalent bond?


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ruveyn
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26 Jun 2011, 3:24 pm

ryan93 wrote:
I'm writing an argument about a particular branch of pseudo-science, and I need to understand the IUPAC definition of a molecule. Unfortunately, I know nothing about Quantum Chemistry...

Quote:
Molecule
An electrically neutral entity consisting of more than one atom (). Rigorously, a molecule, in which must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state.


Does this imply that there needs to be covalent bond?


What about a van der Wall's bond?

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ryan93
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26 Jun 2011, 3:47 pm

ruveyn wrote:
ryan93 wrote:
I'm writing an argument about a particular branch of pseudo-science, and I need to understand the IUPAC definition of a molecule. Unfortunately, I know nothing about Quantum Chemistry...

Quote:
Molecule
An electrically neutral entity consisting of more than one atom (). Rigorously, a molecule, in which must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state.


Does this imply that there needs to be covalent bond?


What about a van der Wall's bond?

ruveyn


Is that what you inferred from the above definition? I've never heard a molecule being defined as a pair or more of atoms with van der waal interactions; in that case a cup of water would be counted as a single molecule.


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ruveyn
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26 Jun 2011, 5:41 pm

ryan93 wrote:

Is that what you inferred from the above definition? I've never heard a molecule being defined as a pair or more of atoms with van der waal interactions; in that case a cup of water would be counted as a single molecule.


I am asking whether a molecule can be held together even in part by a van der Wall bound. I am not a chemist so you could help me out here.

And what about ionic binding?

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ryan93
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26 Jun 2011, 5:57 pm

Oh, sorry. I think some proteins are stablised by v.d.w forces, and at low temperatures v.d.w forces can make stable clusters of molecules, but in general I'm not sure.
As for ionic bonding, it is comfortably used in the more colloquial definition of a molecule, and they often stabilise proteins.

I was hoping you would post, as you seem to be comfortable with the maths behind QM, and the above definition seems to referring to a quantum phenomenon.


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