Acertain ab4 molecule has a square-planar molecular geometry.
which of the following statements about the molecule is or are true?

a. the molecule has four electron domains about the central atom a.
b. the b−a−b angles between neighboring b atoms are 90∘.
c. the molecule has two nonbonding pairs of electrons on atom a.
d. none of the above

 b). The B−A−B angles between neighboring B atoms are 90∘.

Explanation:  The square planar geometry is the geometry in which the four groups are connected through an angle of 90∘ and all 5 atoms are in one plane.

It is not necessary for the molecule to have two non bonding pair of electrons on atom A but if it does have , then its parent geometry will be distorted octahedral. And if it doesn't have this non bonding pair of electrons then the geometry would be the square planar.

Thus the molecule has four electron domains about the central atom A if the parent geometry is square planar otherwise it would have 8 electron domain in distorted octahedral geometry.

the volume increases