How do I determine Formal Charge?


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Rogelio Bazan 1D
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How do I determine Formal Charge?

Postby Rogelio Bazan 1D » Sun May 13, 2018 10:24 pm

So I understand that the equation for the formal charge is the following:
Formal Charge = [# valence electrons on neutral atom] – [(# lone electron pairs) + (½ # bonding electrons)]

What I don't understand is that yes the best formal charge should be the 0 (zero) but there are times in which the octet rule is overruled like the examples in class. I feel like this is what is confusing me the most and I would like some clarification. Thanks. -Roger

Chem_Mod
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Re: How do I determine Formal Charge?

Postby Chem_Mod » Sun May 13, 2018 10:34 pm

Even for the expanded octet structures and octet exception structures, the equation for the formal charge is still the same.

Hannah Lee 1B
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Re: How do I determine Formal Charge?

Postby Hannah Lee 1B » Sun May 13, 2018 11:34 pm

Yes, ideally you would try to draw the molecule in such a way that the formal charge of each atom is 0. However, in cases like an odd number of electrons (ex. NO),
incomplete octets (ex. BF3), or expanded valence shells (atoms with 3d and up), the octet rule can be broken and the formal charges can be not zero, as long as they add up to the molecule's charge.


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