Ncert Exercises & Solutions

Which of the following is isoelectronic pair?

1.	${ICl}_{2}$ , ${ClO}_{2}$	2.	${BrO}_{2}^{-}$ , ${BrF}_{2}^{+}$
3.	${ClO}_{2}$ , $BrF$	4.	${CN}^{-}$ , $O_{3}$

Hint: Isoelectronic species have the same number of electrons.

Isoelectronic pairs have the same number of electrons

	${BrO}_{2}^{-}$	${BrF}_{2}^{+}$
Total number of electrons	35 + 2 $\times$ 8 + 1 = 52	35 + 9 $\times$ 2 – 1 = 52

Hence,(b) is the correct choice, while in another case this value is not equal.

ICl₂	ClO₂
53 + 2 x 17 = 87	17 + 16 = 33

ClO₂	BrF
17 + 16 = 33	35+ 9=44

${CN}^{-}$	O₃
6 + 7 + 1 = 14	8 x 3 = 24

Hence, only (b) is the correct choice