DeusExMachina
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Covalent Bonds and Quantum Physics Stuff
I know this is probably question but I'm wondering how this quantum physics stuff relates to covalent bonds. I know how it works and stuff but I
don't get how they relate. For example, Boron would be 1s<sup>2</sup> 2s<sup>2</sup> 2p<sup>1</sup> because
boron is number 5 so all the superscripts or whatever they are have to add up to five but how does this relate to covalent bonds? Is it the electronic
configuration and the noble gas structure stuff?
[Edited on 7-5-2003 by DeusExMachina]
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Lugh
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from what i can remember, in the case of boron it would try to get 3 more electrons from somewhere e.g. flourine (BF3) in order to bring the number up
to 4 in the p orbital, which would then be half full, e.g. 1s2 2s2 2p4. these electrons are shared between the different atoms. this is a covalent
bond.
having a half full orbital is stable and so its quite happy to stay in this position.
I think this is correct, its been a while since i studied orbitals and bonds 
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Blind Angel
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I don't think that molecul can be happy
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Marvin
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Real molecules are always somewhere between the extreme cases of ionic and covalent.
Looking at ionic, boron has 3 valence electrons to contribute, so it forms B3+ with 3F- ions.
Looking at covalent, boron has 3 valence electrons with which to form covalent bonds, so 1 of each form a bond with 1 each of 3 fluorine atoms. This
gives it 2 electrons short of an octet however, and it is not at all happy. It cant form any more ordinary covalent bonds becuase it doesnt have any
more electrons to use, but it can form a bond provided the atom its forming a bond with supplies both of the electrons for the bond. How is this
possible? Molecules with lone pairs. If you look at ammonia, nitrogen has 5 valence electrons, it needs 3 for its octet, so it bonds with 3 hydrogen
atoms. 2 of those 5 atoms arnt involved in bonding at all, they cant form ordinary bonds with other atoms becuase it nolonger has any unfilled
orbitals to put the extra electrons in. If you mix boron trifluoride and ammonia, the lone pair on the nitrogen, and the missing pair on the boron
form a dative covalent bond, forming NH3BF3. Ammonia is a lewis base (=has a lone pair, and boron trifluoride is a lewis acid (missing pair).
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DeusExMachina
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I just found out that it doesnt have to written out like this all the time 1s<sup>2</sup> 2s<sup>2</sup>
2p<sup>1</sup>
I'll give an example of sodium
2-8-1
_________________________________
this is how it works:
Shell Number: 1 2 3 4 5
Maximum Number of Electrons: 2 8 18 32 50
2-8-1 works because it shows that the whole level is filled for 1, 2 and is just getting started on 3. I know that probably most of you guys know this
but I just thought I'd share it because it seems much more easier than the other way of showing the electronic configuration.
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Marvin
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Its simpler, but its no more useful than simply knowing the number of valence electrons for an atom.
In that view, the last number is the number of valence electrons, and all previos ones are irrelavent, as they never take part in reactions.
You can achieve a simplification that doesnt cripple the chemistry, by only considering the structure of valence electrons.
Sodium is simply [Ne] 3s1
Sulphur is simply [Ne] 3s2 3p4.
The core is literally noble gas like, and the correct one is used to represent its deeper structure.
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