Question

Which of the following species is not tetrahedral?

• A. \( \text{CH}_4 \)
• B. \( \text{SF}_4 \)
• C. \( \text{NH}_4^+ \)
• D. \( \text{SiCl}_4 \)

Hint:

A perfect tetrahedral geometry requires four bonding atoms around the central atom with no lone pairs. Molecules with lone pairs, like \( \text{SF}_4 \), deviate from tetrahedral geometry.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The geometry of a species depends on its hybridization and the presence of lone pairs on the central atom (VSEPR theory).
Step 2: Detailed Explanation:
(A) \( \text{CH}_4 \): Carbon has 4 valence electrons and forms 4 bonds with H. Steric number = 4 (0 lone pairs). Hybridization is \( \text{sp}^3 \). Geometry: Tetrahedral.
(B) \( \text{SF}_4 \): Sulfur has 6 valence electrons. It forms 4 bonds with F and has 1 lone pair. Steric number = 5. Hybridization is \( \text{sp}^3\text{d} \). Geometry: See-saw.
(C) \( \text{NH}_4^+ \): Nitrogen (\( 5-1=4 \) valence electrons) forms 4 bonds with H. Steric number = 4 (0 lone pairs). Hybridization is \( \text{sp}^3 \). Geometry: Tetrahedral.
(D) \( \text{SiCl}_4 \): Silicon has 4 valence electrons and forms 4 bonds with Cl. Steric number = 4 (0 lone pairs). Hybridization is \( \text{sp}^3 \). Geometry: Tetrahedral.
Step 3: Final Answer:
\( \text{SF}_4 \) is not tetrahedral.