Question

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

(a) $-0.75,1.25$

(b) $-0.75,1.0$

(c) $-0.75,0.6$

(d) $-3,1.25$

Answer 1

Correct option of this question will be (A)

Explanation —

Formal charge on an atom $=$ No. of valence electrons – total no. of electrons of lone pairs $-\frac{1}{2}$ [no. of shared electrons]

Thus, for $\mathrm{PO}_4^{3-}$ ions, 3 single bonded oxygen atoms have formal charge $=-1$ and double bonded oxygen has formal charge $=0$.

Formal charge on $\mathrm{O}$ atoms $=\frac{-3}{4}=-0.75$

$\mathrm{P}-\mathrm{O}$ bond order $=\frac{5}{4}=1.25$

(5 bonds between 4 oxygen atoms)