Question

The ion that is isoelectronic with $CO$ is

• A. $O^{+}_2$
• B. $O^{-}_2$
• C. $CN^{-}$
• D. $N_2$

Answer 1

Answer: (C)

Isoelectronic species are those species, which have same number of electrons.
Total number of electrons in $CO$ is $= 6 + 8= 14$
(a) Total number of electrons in $O^{+}_2$ is $= 8 + 8 -1 = 15$
(b) Total number of electrons in $CN^{-}$ is $= 6 + 7+1= 14$
(c) Total number of electrons in $O^{-}_2$ is $= 8 + 8+1= 17$
(d) Total number of electrons in $N^{+}_2$ is $= 7 + 7 -1 = 13$
Thus, $CN^{-}$ is isoelectronic with $CO$.