Which one of the following elements have a unique property to form `p pi-p pi` multiple bonds with itself ?

Options

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

Answer

To solve the question of which element has the unique property to form `p pi-p pi` multiple bonds with itself, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which of the given elements can form `p pi-p pi` multiple bonds with itself. The elements provided are nitrogen, phosphorus, arsenic, and bismuth.

2. **Identifying the Elements**:
- **Nitrogen (N)**: Atomic number 7, located in period 2.
- **Phosphorus (P)**: Atomic number 15, located in period 3.
- **Arsenic (As)**: Atomic number 33, located in period 4.
- **Bismuth (Bi)**: Atomic number 83, located in period 6.

3. **Understanding `p pi-p pi` Bonds**:
- `p pi-p pi` bonds are formed by the overlap of p orbitals. For an element to form these bonds with itself, it should ideally not have d orbitals available for bonding, which are present in elements from the third period onwards.

4. **Analyzing Each Element**:
- **Nitrogen**: Being in the second period, nitrogen has only p orbitals available and can form a triple bond with itself (N≡N) through `p pi-p pi` bonding.
- **Phosphorus**: In the third period, phosphorus can utilize d orbitals, which allows for different types of bonding, including `d pi-p pi` bonds.
- **Arsenic**: Similar to phosphorus, arsenic can also use d orbitals for bonding.
- **Bismuth**: Like arsenic and phosphorus, bismuth has d orbitals available for bonding.

5. **Conclusion**: Since only nitrogen is in the second period and can form `p pi-p pi` bonds with itself without the involvement of d orbitals, it is the unique element that meets the criteria.

### Final Answer:
**Nitrogen (N)** is the element that has the unique property to form `p pi-p pi` multiple bonds with itself.