Question

Assertion (A) $SF _{4}$ molecule has two type of structure.

in which structure (b) is more stable than (a).
Reason (R) $l p-b p$ repulsions decide the greater stability of structure (b).

• A. Both $A$ and $R$ are correct; $R$ is the correct explanation of $A$.
• B. Both $A$ and $R$ are correct; $R$ is not the correct explanation of $A$.
• C. $A$ is correct; $R$ is incorrect.
• D. $A$ is incorrect; $R$ is correct.

Answer 1

Answer: (A)

In (a), the lone pair is present at axial position, so there are three $l p-b p$ repulsions at $90^{\circ}$. In (b) the lone pair is at equatorial position and there are two $l p-b p$ repulsions. Hence, arrangement (b) is more stable.
The shape shown in (b) is described as a distorted tetrahedron, a folded square or a see-saw.
Thus, both $A$ and $R$ are correct; $R$ is the correct explanation of $A$.