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 determine the number of unpaired electrons in the valence shell of group 15 elements (nitrogen, phosphorus, arsenic, antimony, and bismuth), we can follow these steps:

### Step 1: Identify the Group 15 Elements
Group 15 elements include:
- Nitrogen (N)
- Phosphorus (P)
- Arsenic (As)
- Antimony (Sb)
- Bismuth (Bi)

### Step 2: Write the Electronic Configurations
The electronic configurations for the valence shell of these elements can be represented as follows:
- Nitrogen (N): \(1s^2 2s^2 2p^3\) → Valence shell: \(ns^2 np^3\)
- Phosphorus (P): \(1s^2 2s^2 2p^6 3s^2 3p^3\) → Valence shell: \(ns^2 np^3\)
- Arsenic (As): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^3\) → Valence shell: \(ns^2 np^3\)
- Antimony (Sb): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^3\) → Valence shell: \(ns^2 np^3\)
- Bismuth (Bi): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^3\) → Valence shell: \(ns^2 np^3\)

### Step 3: Determine the Number of Unpaired Electrons
In the valence shell configuration \(ns^2 np^3\), the \(ns^2\) part indicates that there are 2 paired electrons in the s-orbital. The \(np^3\) part indicates that there are 3 electrons in the p-orbital. According to Hund's rule, these 3 p electrons will occupy separate p orbitals before pairing up. Therefore, all three p electrons remain unpaired.

Thus, for each of the group 15 elements:
- Nitrogen (N): 3 unpaired electrons
- Phosphorus (P): 3 unpaired electrons
- Arsenic (As): 3 unpaired electrons
- Antimony (Sb): 3 unpaired electrons
- Bismuth (Bi): 3 unpaired electrons

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

### Final Answer
**3**