The pronounced change from non-metallic behaviour and also increase in the basicity of oxides from nitrogen to bismuth in group `15` is principally due to incresing size of the atoms. The ionisation potential of nitrogen is very high on account of its small size. However, ionisation potential decreases regularly on descending the group.
In all the group `15` elements, the number of unpaired electrons in the valence shell is.

Options

A. 2
B. 3
C. 4
D. 5

Explanation

To solve the question regarding the number of unpaired electrons in the valence shell of group 15 elements, we can follow these steps:

### Step 1: Identify the Group 15 Elements
Group 15 elements include nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).

### Step 2: Determine the Electronic Configuration
The general electronic configuration for group 15 elements can be represented as \( ns^2 np^3 \). This means:
- Nitrogen: \( 1s^2 2s^2 2p^3 \)
- Phosphorus: \( 1s^2 2s^2 2p^6 3s^2 3p^3 \)
- Arsenic: \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4p^3 \)
- Antimony: \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4p^6 5s^2 5p^3 \)
- Bismuth: \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4p^6 5s^2 5p^6 6s^2 6p^3 \)

### Step 3: Count the Unpaired Electrons
In the outermost shell (valence shell), we focus on the \( np^3 \) configuration:
- For nitrogen: \( 2p^3 \) has 3 unpaired electrons.
- For phosphorus: \( 3p^3 \) has 3 unpaired electrons.
- For arsenic: \( 4p^3 \) has 3 unpaired electrons.
- For antimony: \( 5p^3 \) has 3 unpaired electrons.
- For bismuth: \( 6p^3 \) has 3 unpaired electrons.

### Step 4: Conclusion
All group 15 elements have 3 unpaired electrons in their valence shell.

### Final Answer
The number of unpaired electrons in the valence shell of all group 15 elements is **3**.

---