Choose the correct answer

Options

A. Both `(CH_3 )_3 N` and `(SiH_3 )_3 N` are pyramidal
B. Both `(CH_3 )_3 N` and `(SiH_3 )_3 N` are triangular planar
C. `(CH_3 )_3 N` is pyramidal and `(SiH_3 )_3 N` is triangular
D. `(CH_3 )_3 N` is triangular and `(SiH_3 )_3 N` is pyramidal

Answer

To solve the question, we need to analyze the options provided regarding the structures and hybridizations of tri-methyl-nitrogen and tri-silial-nitrogen.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- The first compound is tri-methyl-nitrogen, which can be represented as (CH₃)₃N.
- The second compound is tri-silial-nitrogen, which can be represented as (SiH₃)₃N.

2. **Analyze Tri-methyl-nitrogen**:
- Tri-methyl-nitrogen has three methyl groups (CH₃) attached to a nitrogen atom (N).
- The nitrogen atom has one lone pair of electrons and forms three sigma bonds with the three methyl groups.
- **Hybridization**: The nitrogen atom undergoes sp³ hybridization because it has one lone pair and three sigma bonds.
- **Shape**: The presence of the lone pair leads to a trigonal pyramidal shape.

3. **Analyze Tri-silial-nitrogen**:
- Tri-silial-nitrogen consists of three silicon atoms (Si) bonded to a nitrogen atom (N).
- In this case, the nitrogen's lone pair is involved in bonding with silicon due to silicon's ability to utilize its vacant d-orbitals.
- **Hybridization**: Since there are no lone pairs left on nitrogen after bonding with silicon, and it forms three sigma bonds, the hybridization is sp².
- **Shape**: The arrangement of the three silicon atoms around the nitrogen leads to a trigonal planar shape.

4. **Compare the Structures**:
- Tri-methyl-nitrogen is pyramidal due to the lone pair on nitrogen.
- Tri-silial-nitrogen is planar because of the absence of lone pairs on nitrogen and the sp² hybridization.

5. **Choose the Correct Statement**:
- Based on the analysis, the correct statement is that tri-methyl-nitrogen is pyramidal and tri-silial-nitrogen is planar. Therefore, the correct option is option 3.