1 Answer
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Formal charges ….
Formal charges are assigned to individual atoms in a compound. Formal charges are not actual charges, they are hypothetical charges, assuming that all of the bonds are 100% covalent (Similarly, oxidation states are hypothetical charges assuming that all the bonds are 100% ionic. There are no 100% ionic bonds.) The sum of the formal charges must equal the total charge on the particle, zero for a compound, the ioniz charge for a polyatomic ion.
Formal charge = valence electrons – nonbonding electrons – 1/2 bonding electrons
FC = VE – NBE – 1/2BE
:C≡O: ……. FC of C = 4 – 2 – 3 = -1…… FC of O = 6 – 2 – 3 = +1
O=C=O …. FC of C = 4 – 0 – 4 = 0 …… FC of O = 6 – 4 – 2 = 0
O−C=O (2-) …. plus two additional resonance structures
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…..O
FC of C = 4 – 0 – 4 = 0
FC of O in C=O = 6 – 4 -2 = 0
FC of O in C−O = 6 – 6 – 1 = -1 ….. Since there are two of these oxygen atoms, the total of the FCs equals the charge on the ion, -2.
