In PO43- ion the formal charge on the oxygen atom of P--O bond

Home Work Help
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1

In PO43- ion the formal charge on the oxygen atom of P–O bond is
a, +1
b. +0.75
c. -1
d. -0.75
please give detail how to calculate it

2

Formal charge on an atom = (Total no. of valence electrons) -(No. of lone pairs + 1/2 X no. of bonding electrons)
Formal charge on oxygen = 6 - [ 6+(1/2 X 2)]
= 6 - 7
= -1
There are total 3 Oxygen having charge hence -1 X 3 = -3
Now the formal charge of oxygen = Formal charge of each oxygen/total no. of oxygen atoms
= -3/4
= - 0.75