practice passage at the end of chapter 2 (gen/orgo chem)

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aabowman98
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Joined: Tue Oct 01, 2019 2:53 pm

practice passage at the end of chapter 2 (gen/orgo chem)

Post by aabowman98 » Tue Oct 08, 2019 3:40 pm

I don't at all understand how to use the diagram and for the most part can't answer these questions. Please help
aabowman98
Posts: 4
Joined: Tue Oct 01, 2019 2:53 pm

Re: practice passage at the end of chapter 2 (gen/orgo chem)

Post by aabowman98 » Tue Oct 08, 2019 3:41 pm

also, why in problem 2 do we know that for each molecule (i.e. elemental oxygen, superoxide, and peroxide) that 8 electrons are in bonding MO's ?
NS_Tutor_Mathias
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Joined: Sat Mar 30, 2019 8:39 pm

Re: practice passage at the end of chapter 2 (gen/orgo chem)

Post by NS_Tutor_Mathias » Wed Oct 09, 2019 11:35 am

Here is a filled-in version of the diagram for O2: https://www.quora.com/Why-is-the-molecu ... N%E2%82%82

As you can see, you really just line up first the s-shells opposite each other then then p-shells opposite each other, then fill the whole thing up bottom-to-top (lowest to highest energy) and following Hund's rule and the Pauli exclusion principle. You then call the 'top' ones 'anti-bonding orbitals' and the bottom ones bonding orbitals, and now you can use this diagram to determine bond orders in a molecule (with the formula from the passage, ([bonding]-[antibonding])/2 ) and as an added bonus you can see if there are any unpaired electrons present in your molecular orbital diagram and thereby predict paramagnetism vs diamagnetism.

The diagram shown is supposed to be a not-filled-out-yet version of such a molecular orbital diagram, but I suspect there is also a small error at the bottom with the sigma orbitals. From what I hear, these things are currently being reworked both content wise and graphically, so in the future they should be far clearer and easier to read!
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