Question

the formal charge and p-o bond order in po4 3- respectively are​

Answer 1

Answer:

Be sure not to confuse formal charge with oxidation number. In the phosphate ion, P has an oxidation number of +5 and each oxygen has an oxidation number of -2. Oxidation state is the charge on an element if all the bonds are 100% ionic, which of course, we know they are not.

Formal charge is the charge on an element as if all of the bonds are 100% covalent, which they are not. The bonds are actually polar. The sum of the formal charges must equal zero for a compound or the charge on the ion. Formal charge is calculated from the following....

FC = VE - NBE - ½BE ..... where VE = valence electrons, NBE= nonbonding electrons, and BE = bonding electrons

......O ..... each oxygen has three lone pairs

.......|

O − P − O ...... FC(P) = 5 - 0 - 4 = +1

.......|

..... O ....... FC(O) = 6 - 6 - 1 = -1

Ideally, the formal charges should be as close to zero as possible. Therefore, creating a double bond will give one oxygen a FC of 0, and reduce the FC of P to zero. But all of the bonds in PO4^3- are identical. Therefore, the only way to represent this with Lewis structures is four resonance structures.

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