The correct order of radii of C, N, P, S follows the order

Options

A. `N lt C lt P lt S`
B. `C lt N lt S lt P`
C. `C lt N lt P lt S`
D. `N lt C lt S lt P`

Answer

To determine the correct order of radii for Carbon (C), Nitrogen (N), Phosphorus (P), and Sulphur (S), we need to analyze their positions in the periodic table and apply the trends in atomic radii.

### Step-by-Step Solution:

1. **Identify the Position of Elements**:
- Nitrogen (N) is in Group 15 and Period 2.
- Carbon (C) is in Group 14 and Period 2.
- Phosphorus (P) is in Group 15 and Period 3.
- Sulphur (S) is in Group 16 and Period 3.

2. **Understand the Trends in Atomic Radii**:
- **Across a Period**: Atomic radius decreases from left to right due to the increase in nuclear charge, which pulls the electrons closer to the nucleus.
- **Down a Group**: Atomic radius increases as we move down a group because additional electron shells are added, which outweighs the effect of increased nuclear charge.

3. **Compare the Sizes**:
- Between Nitrogen (N) and Carbon (C): Since both are in Period 2, and Carbon is to the right of Nitrogen, Carbon will have a larger radius than Nitrogen. Therefore, N < C.
- Between Phosphorus (P) and Sulphur (S): Both are in Period 3, but Sulphur is to the right of Phosphorus, so Sulphur will have a smaller radius than Phosphorus. Therefore, S < P.

4. **Combine the Findings**:
- From the above comparisons, we can summarize:
- N < C (from Period 2)
- S < P (from Period 3)
- Now, we need to compare the elements from different periods:
- Since Nitrogen (N) is in Period 2 and Phosphorus (P) is in Period 3, we expect P to be larger than N.
- Similarly, Carbon (C) is also in Period 2 and will be smaller than Phosphorus (P) but larger than Nitrogen (N).

5. **Final Order of Radii**:
- Based on the comparisons, the correct order of atomic radii from smallest to largest is:
- N < C < S < P

### Conclusion:
The correct order of radii for the elements is:
**N < C < S < P**