2B. 23


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VLi_2B
Posts: 99
Joined: Sat Sep 14, 2019 12:15 am

2B. 23

Postby VLi_2B » Sun Oct 27, 2019 12:59 am

2B.23 Determine the formal charge on each atom in the following molecules. Identify the structure of lower energy in each pair. (The pictures are in the textbook on page 87)

Can someone please explain formal charges to me?

Eugene Chung 3F
Posts: 142
Joined: Wed Nov 15, 2017 3:03 am

Re: 2B. 23

Postby Eugene Chung 3F » Sun Oct 27, 2019 2:08 am

Formal charge of an atom indicates gain/loss of electrons while forming covalent bond. So, to assign formal charge of an atom, first, determine the number of valence electrons for each bound atom, then compare the number of bounding (shared, S) electron and the number of lone pairs (L) of free atom by using this formula: FC = V - (L+S/2).

MaggieHan1L
Posts: 100
Joined: Thu Jul 11, 2019 12:17 am

Re: 2B. 23

Postby MaggieHan1L » Sun Oct 27, 2019 1:52 pm

The preferred formal charge is 0. When he gave the example of sulphate SO4, the lewis structure was technically correct but the formal charges weren't ideal. We use formal charge to give us better lewis dot structures. When you're drawing lewis dot structures and you can't get all of the formal charges to 0 you should have the more electronegative/higher electron affinity element have the negative formal charge.


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