Question

Pick out the isoelectronic structure from the following:
I : ${CH}_3^{+}$
II : $H_3{O}^{+}$
III : ${NH}_3$
IV: ${CH}_3^{-}$

• A. I and II
• B. III and IV
• C. I and III
• D. II, III and IV

Answer 1

Answer: (D)

II, III and IV

$C{H}_3^{+}$ is $s{p}^2$ hybridised. Therefore, the structure is a trigonal planar.

$H_3{O}^{+}$ is $s{p}^3$ hybridised. Therefore, the structure is trigonal pyramidal.

$N{H}_3$ is $s{p}^3$ hybridised therefore, the structure is trigonal pyramidal.

$C{H}_3^{-}$ is $s{p}^3$ hybridised therefore, the structure is trigonal pyramidal.

$II,III,IV$ has one lone pair and three bonds(10 electrons in total) so all three structures are similar.

Since they have an equal number of electrons, they are isoelectronic species.