Question

Which of the following pair of species have definite geometry?

• A. SF$_4$ and BF$_4^-$
• B. BF$_4^-$ and CF$_4$
• C. BF$_3$ and SO$_2$
• D. COCl$_2$ and CO$_3^{2-}$

Answer 1

Answer: (B), (D)

BF$_4^-$ and CF$_4$

Answer 2

All listed species have definite geometries. The question likely implies pairs with the same definite geometry or ideal definite geometry.

1. BF$_4^-$: Tetrahedral (ideal).

2. CF$_4$: Tetrahedral (ideal).

   • Pair (BF$_4^-$ and CF$_4$) has the same ideal geometry.

3. COCl$_2$: Trigonal planar (ideal).

4. CO$_3^{2-}$: Trigonal planar (ideal).

   • Pair (COCl$_2$ and CO$_3^{2-}$) has the same ideal geometry.

Since both option 2 and option 4 consist of species with the same ideal geometry, and the question asks for "definite geometry", both pairs are valid. However, in a single-choice context, option 2 (BF$_4^-$ and CF$_4$) is often presented as a primary example of identical tetrahedral geometry.