Question

If anion has see-saw shape, then the shape of cation formed is:
A) Linear
B) Bent
C) Pentagonal bipyramidal
D) Trigonal planar

Answer 1

First let us determine the steric number of the central atom in the cation. Then let us determine the type of geometry and the hybridization.

Complete answer:
You can represent the cation with the chemical formula ${\text{ACl}}_4^ -$ . The central atom in the cation has one lone pair of electrons and four bond pairs of electrons. The steric number is $4 + 1 = 5$
The steric number of 5 is associated with $s{p^3}d$ and electron pair geometry of trigonal bipyramidal. The ionic geometry is see-saw.

You can represent the cation with the chemical formula ${\text{DCl}}_2^ +$ . The central atom in the cation has zero lone pair of electrons and two bond pairs of electrons. The steric number is $0 + 2 = 2$
The steric number of 2 is associated with $sp$ and electron pair geometry of linear. The ionic geometry is also linear. Thus, if cation has see-saw shape, then the shape of cation formed is linear.

Hence, the option (A) is the correct answer.

Note: Steric number is the sum of the number of lone pairs and the bond pairs of electrons. You can use the steric number to determine the type of hybridization and geometry. The electron pair geometry can be the same as the molecular/ionic geometry if the number of lone pairs of electrons is zero. For non-zero numbers of lone pairs of electrons, the electron pair geometry and the molecular/ionic geometries are different.