The incorrect statement among the following is

Options

A. Reducing character of hydrides of group 15 increases down the group
B. Basicity of hydrides of group 15 increases down the group
C. Phosphorus and arsenic can form `p pi- d pi` bond
D. `NCl_(5)` does not exist

Answer

To determine the incorrect statement among the given options regarding the hydrides of group 15 elements, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "Reducing character of hydrides of group 15 increases down the group."
- As we move down the group from NH3 (ammonia) to BiH3 (bismuth hydride), the reducing character does indeed increase. This is because heavier hydrides tend to lose hydrogen more easily, thus increasing their reducing ability.
- **Conclusion**: This statement is **correct**.

2. **Statement 2**: "Basicity of hydrides of group 15 increases down the group."
- The basicity of hydrides generally decreases down the group. For example, NH3 is a strong base, while BiH3 is much weaker. This is due to the decreasing electronegativity and increasing size of the central atom, which makes it less able to donate a lone pair of electrons.
- **Conclusion**: This statement is **incorrect**.

3. **Statement 3**: "Phosphorus and arsenic can form P-Pi-D-Pi bonds."
- Phosphorus and arsenic can indeed form P-Pi-D-Pi bonds because they have available d-orbitals that can participate in bonding. This allows for the formation of such bonds.
- **Conclusion**: This statement is **correct**.

4. **Statement 4**: "NCl5 does not exist."
- Nitrogen, being a second-period element, can form a maximum of four bonds due to the absence of d-orbitals. Therefore, NCl5 cannot exist as nitrogen cannot accommodate five bonds.
- **Conclusion**: This statement is **correct**.

### Final Conclusion:
The incorrect statement among the options is **Statement 2**: "Basicity of hydrides of group 15 increases down the group."