Which of the following. has the highest `p pi` -`p pi` bonding tendency?

Options

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

Explanation

To determine which element has the highest pπ-pπ bonding tendency, we need to analyze the bonding characteristics of the given elements, focusing on their atomic size and the number of valence electrons.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements in question are likely to be Nitrogen (N), Phosphorus (P), Arsenic (As), and Antimony (Sb).

2. **Count Valence Electrons**:
- Nitrogen has 5 valence electrons (2s² 2p³).
- Phosphorus has 5 valence electrons (3s² 3p³).
- Arsenic has 5 valence electrons (4s² 4p³).
- Antimony has 5 valence electrons (5s² 5p³).

3. **Consider Atomic Size**:
- Nitrogen is the smallest of these elements, followed by Phosphorus, Arsenic, and then Antimony. The size increases down the group.

4. **Analyze pπ-pπ Bonding**:
- pπ-pπ bonding occurs when p orbitals overlap. Smaller atoms with p orbitals can overlap more effectively due to closer proximity.
- Nitrogen, being the smallest, has a high tendency for pπ-pπ bonding because its p orbitals can overlap effectively, forming strong bonds (like in N₂).

5. **Evaluate Lone Pairs and Repulsions**:
- In nitrogen, the small size leads to significant repulsion between lone pairs, but it also allows for effective bonding due to the formation of multiple bonds (like the triple bond in N₂).
- Larger atoms like Phosphorus, Arsenic, and Antimony have larger atomic sizes, which reduces the effectiveness of pπ-pπ bonding due to increased distance and the presence of d-orbitals.

6. **Conclusion**:
- Based on the above analysis, Nitrogen has the highest pπ-pπ bonding tendency due to its small size, effective overlap of p orbitals, and the ability to form strong multiple bonds.

### Final Answer:
**Nitrogen (N) has the highest pπ-pπ bonding tendency.**