The following can exist as a diatomic molecule

Options

A. N
B. P
C. As
D. Bi

Answer

To determine which of the elements can exist as a diatomic molecule among nitrogen, phosphorus, arsenic, and bismuth, we will analyze each element based on their atomic structure and bonding capabilities.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements in question are nitrogen (N), phosphorus (P), arsenic (As), and bismuth (Bi).

2. **Analyze Nitrogen**:
- **Atomic Number**: Nitrogen has an atomic number of 7.
- **Electron Configuration**: Its electron configuration is 1s² 2s² 2p³.
- **Bonding**: Nitrogen has three unpaired electrons in its p-orbitals, allowing it to form three bonds with another nitrogen atom. This results in the formation of a diatomic molecule (N₂) through the formation of a triple bond (one sigma bond and two pi bonds).

3. **Analyze Phosphorus**:
- **Atomic Number**: Phosphorus has an atomic number of 15.
- **Electron Configuration**: Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p³.
- **Bonding**: Although phosphorus can form bonds, it typically forms tetrahedral structures (like P₄) rather than diatomic molecules due to its larger atomic size, which makes p-p bonding less effective.

4. **Analyze Arsenic**:
- **Atomic Number**: Arsenic has an atomic number of 33.
- **Electron Configuration**: Its electron configuration is [Ar] 3d¹⁰ 4s² 4p³.
- **Bonding**: Similar to phosphorus, arsenic tends to form larger molecules (like As₄) and does not readily form diatomic molecules due to its size and bonding characteristics.

5. **Analyze Bismuth**:
- **Atomic Number**: Bismuth has an atomic number of 83.
- **Electron Configuration**: Its electron configuration is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³.
- **Bonding**: Bismuth is a metal and primarily forms metallic bonds. It does not exist as a diatomic molecule.

6. **Conclusion**: Based on the analysis, only nitrogen can exist as a diatomic molecule (N₂). Phosphorus, arsenic, and bismuth do not form diatomic molecules under normal conditions.

### Final Answer:
The following can exist as a diatomic molecule: **Nitrogen (N₂)**.