Question

Of the following sets which one does not contain isoelectronic species ?

• A. $B{O}_3^{3-},C{O}_3^{2-},N{O}_3^{-}$
• B. $S{O}_3^{2-},C{O}_3^{2-},N{O}_3^{-}$
• C. $C{N}^{-},N_2,C_2^{2-}$
• D. $P{O}_4^{3-},S{O}_4^{2-},CI{O}_4^{-}$

Answer 1

Answer: (B)

Species	Electron in central element	Electrons in other element	Charge gained	Total
$B{O}_3^{3-}$	$5$	$3\times 8=24$	$+3$	$32$
$C{O}_3^{2-}$	$6$	$3\times 8=24$	$+2$	$32$
$N{O}_3^{-}$	$7$	$3\times 8=24$	$+1$	$32$
$S{O}_3^{2-}$	$16$	$3\times 8=24$	$+2$	$42$
$C{N}^{-}$	$6$	$7$	$1$	$14$
$N_2$	$7$	$7$	$0$	$14$
$C_2^{2-}$	$6$	$6$	$+2$	$14$
$P{O}_4^{3-}$	$15$	$4\times 8=32$	$+3$	$50$
$S{O}_4^{-}$	$16$	$4\times 8=32$	$+2$	$50$
$CI{O}_3^{2-}$	$17$	$4\times 8=32$	$+1$	$50$

Thus (a) $B{O}_3^{3-},C{O}^{2-},N{O}_3$ are isoelectronic.
(b) $S{O}_3^{2-},C{O}_3^{2-},N{O}_3^{-}$ are not isoelectronic.