TBR CBT 5 BS Question 101

[Sailor Senshi Dermystify]

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Hello I have a question about oxidation state. I am not seeing how the Carbonyl Oxygen is +3, the methyl group is -3 and the C in CO2 is +4.

Any help will be greatly appreciated.

See the question with explanations attached.

 

[quicheduty]

Remember you assign oxidation states based on electronegativity, so the more EN atom gets -1 and the less EN gets +1. The carbonyl C has one bond to the more electronegative S, so give C a +1; two bonds to the more electronegative O, so +2, one per bond. C to C gives +0 since they are the same atom and therefore have the same electronegativity. In total the carbonyl C is +3.

In CH4, C is more electronegative than H so with 4 H's, you get -4 on the C.

Knowing this it should make sense why C is +4 in CO2!

 

[Sailor Senshi Dermystify]

Ahh, I get it now 🙂. Thanks, and that's not how I do oxidation states. I thought you have to consider the amount of valence electrons, and then the amount of lone pairs around the atom. When I did that I couldn't see where they got these numbers from.

Thanks again! 🙂