Question

In $P{O}_4^{3-}$ ion, the formal charge on each oxygen atom and $P-O$ bond order respectively are :

• A. -0.75, 1.25
• B. -0.75, 1.0
• C. -0.75, 0.6
• D. -3.1, 25

Answer 1

Answer: (A)

$P-O$ bond order
$=\frac{\text{ Number of bonds in all possible direction between two atoms }}{\text{ Total number of resonating structures }}$
Average formal charge on each of the oxygen atom in calculated as follows:
(i) Total number of electrons present in valence shell of
$P-O=5+8=13$
(ii) Number of electron involved in bond formation
$=13-3$
$=\frac{5}{4}=1.25$
$=\frac{2+1+1+1}{4}$
$=\frac{5}{4}$
Resonating structures are

Total charge on $P{O}_4^{3-}$ ion is $-3$
$=\frac{\text{ Total charge }}{\text{ Total entity of }O\text{-atom }}$
So, the average formal charge on each O-atom is
$=-\frac{3}{4}=-0.75$