Octet exceptions and double bonds

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Casey Monahan 2C
Posts: 18
Joined: Wed Sep 21, 2016 2:57 pm

Octet exceptions and double bonds

Postby Casey Monahan 2C » Sat Oct 22, 2016 11:41 am

How do we know when to use a double bond with exceptions to the octet rule (like with XeOF(4))? Does it have to do with the future charge?

Shirley_Zhang 3O
Posts: 35
Joined: Wed Sep 21, 2016 2:56 pm

Re: Octet exceptions and double bonds

Postby Shirley_Zhang 3O » Sat Oct 22, 2016 1:10 pm

I think it does have to do with the formal charges. The lewis structure for XeOF4 has FC of zero.
One important thing to note is that having a negative partial charge is not preferable because the surrounding atoms have higher electron affinity.

Casey Monahan 2C
Posts: 18
Joined: Wed Sep 21, 2016 2:57 pm

Re: Octet exceptions and double bonds

Postby Casey Monahan 2C » Sat Oct 22, 2016 1:26 pm

That makes sense. Thank you!

Carolyn Huh 1K
Posts: 21
Joined: Wed Sep 21, 2016 2:59 pm

Re: Octet exceptions and double bonds

Postby Carolyn Huh 1K » Sun Oct 23, 2016 2:18 pm

According to the textbook starting from page 85, it states that "phosphorus, sulfur, chlorine, or another nonmetal in Period 3 and subsequent periods can accommodate more than eight electrons in its valence shell". Also, species with radicals and biradicals can have more electrons, and "when the central atom in a molecule has empty d-orbitals, it may be able to accommodate 10, 12 or even more electrons. The elements in such an expanded valence shell may be present as lone pairs or may be used by the central atom to form additional bonds". Additionally, boron and aluminum are two elements in group 13 that may possess unusual Lewis structures in which they contain incomplete octets or halogen atoms acts as bridges.


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