Question

In PO4 3– ion the formal charge on the oxygen atom of P–O bond is
(i) + 1
(ii) – 1
(iii) – 0.75
(iv) + 0.75
how to solve this in easier manner

Answer 1

charge on oxygen is always -2 and total charge in this ion should be -3
so -2*4+charge on p= -3
charge on p= +5
charge on po bond = 5-2=3

Answer 2

In $P O_{4}^{3-}$ ion the formal charge on the oxygen atom of P–O bond is 0.75.

Explanation:

The formula charge can calculated by the following formula:

Formula charge of an atom= (Total number of valence electrons) - (Number of lone pairs +  1/2 × Number of bond pairs

Oxygen has six valence electrons and number of bond pairs in $P O_{4}^{3-}$ ion is six.

Substitute the all values:

Formula charge on oxygen$= 6-\left[6 \times\left(\frac{1}{2} \times 2\right)\right]$

=6-7= -1

Three oxygen atoms in $P O_{4}^{3-}$ ion has -1 charge = $-1 \times 3=-3$

Formal charge of oxygen $=\frac{\text {Formal charge of each oxygen}}{\text {Total number } f \text { oxygen atoms }}$

$=\frac{-3}{4}=-0.75$