Ammonia is iso-structural with:

Options

A. Carbanion
B. Free radical
C. Carbocation
D. None of these

Answer

To determine which species is iso-structural with ammonia (NH3), we need to analyze the structure of ammonia and compare it with the given options: carbanion, free radical, and carbocation.

### Step-by-Step Solution:

1. **Understand the Structure of Ammonia (NH3)**:
- Ammonia has a trigonal pyramidal shape due to the presence of a lone pair of electrons on the nitrogen atom.
- The nitrogen atom is bonded to three hydrogen atoms and has one lone pair. This gives it a total of four electron pairs around the nitrogen, leading to a tetrahedral electron pair geometry, but the molecular shape is trigonal pyramidal.

2. **Analyze the Carbanion (e.g., CH3⁻)**:
- A carbanion like CH3⁻ has a carbon atom with a negative charge and one lone pair of electrons.
- The carbon atom is bonded to three hydrogen atoms, similar to ammonia.
- The structure of CH3⁻ is also trigonal pyramidal due to the lone pair on carbon, making it iso-structural with NH3.

3. **Analyze the Free Radical (e.g., CH3•)**:
- A free radical like CH3• has a carbon atom with one unpaired electron.
- The carbon atom is still bonded to three hydrogen atoms, but the presence of the unpaired electron does not create a lone pair.
- The geometry of CH3• is trigonal planar, which is different from the trigonal pyramidal shape of NH3.

4. **Analyze the Carbocation (e.g., CH3⁺)**:
- A carbocation like CH3⁺ has a carbon atom with a positive charge and only three bonds (no lone pairs).
- This results in a trigonal planar geometry, which is also different from the trigonal pyramidal shape of NH3.

5. **Conclusion**:
- Among the options, only the carbanion (CH3⁻) has a structure that is iso-structural with ammonia (NH3).
- Therefore, the correct answer is **carbanion**.

### Final Answer:
Ammonia is iso-structural with **carbanion (CH3⁻)**.