Expanded Octets

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Malik Oda 1F
Posts: 51
Joined: Thu Jul 25, 2019 12:15 am

Expanded Octets

Postby Malik Oda 1F » Wed Nov 06, 2019 11:31 am

How do I identify an expanded octet and how would I approach drawing the Lewis Structure?

SGonzales_3L
Posts: 55
Joined: Thu Jul 11, 2019 12:17 am

Re: Expanded Octets

Postby SGonzales_3L » Wed Nov 06, 2019 11:34 am

One rule of thumb is to calculate the number of valence electrons in a molecule. Fulfill the octet rule for every atom in the Lewis structure. If you still have some electrons left over, it is highly likely that there is an atom with an expanded octet. Usually elements in the p-block, in period 3 or higher can accommodate expanded octets. Thus, add lone pairs of electrons to those atoms within a molecule and as always, calculate the formal charge.

Brooke Yasuda 2J
Posts: 102
Joined: Sat Jul 20, 2019 12:17 am

Re: Expanded Octets

Postby Brooke Yasuda 2J » Wed Nov 06, 2019 11:36 am

Most of the time when you have a molecule that can form an expanded octet, such as Xenon, you know that it has eight valance electrons. In bonding, you're trying to reduce formal charge, so you can form double bonds between Xenon and other atoms to reduce the formal charge as much as possible.

Robert Tran 1B
Posts: 118
Joined: Thu Jul 11, 2019 12:15 am

Re: Expanded Octets

Postby Robert Tran 1B » Wed Nov 06, 2019 1:01 pm

Expanded octets would be used if it's clear that there is more than 4 atoms bonded to the central atom (ex: XeF5). Also, the octet can be expanded if the formal charge favors it in the lewis structure.

thanh24mai
Posts: 50
Joined: Thu Jul 25, 2019 12:17 am

Re: Expanded Octets

Postby thanh24mai » Wed Nov 06, 2019 2:14 pm

You may sometimes need to expand an octet if you want to ensure you have drawn the most stable lewis structure.

LBacker_2E
Posts: 104
Joined: Wed Sep 18, 2019 12:21 am
Been upvoted: 1 time

Re: Expanded Octets

Postby LBacker_2E » Wed Nov 06, 2019 2:58 pm

Overall, if an expanded octet can be formed (is past 2p orbitals) to yield lower formal charges on the central atom, will this always be a more stable structure?

Doreen Liu 4D
Posts: 54
Joined: Wed Sep 11, 2019 12:17 am

Re: Expanded Octets

Postby Doreen Liu 4D » Wed Nov 06, 2019 2:59 pm

For some elements, expanded octets are not allowed (i.e. some period 2 elements), so just be careful when you're drawing those.


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