Which one of the following elements forms double or triple bond involving `p pi- p pi` bonding?

Options

A. Carbon
B. Silicon
C. Germanium
D. Tin

Answer

To determine which element forms double or triple bonds involving pπ-pπ bonding, we can analyze the given options: carbon, silicon, germanium, and tin.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements in question are carbon (C), silicon (Si), germanium (Ge), and tin (Sn). All these elements belong to Group 14 of the periodic table.

2. **Understand pπ-pπ Bonding**: pπ-pπ bonding occurs when p orbitals from two atoms overlap laterally. This type of bonding is essential for the formation of double and triple bonds.

3. **Consider Atomic Size**: As we move down the group from carbon to tin, the atomic size increases. This increase in size affects the ability of the p orbitals to overlap effectively.

4. **Evaluate Carbon**: Carbon has a small atomic size (atomic number 6) and has the electronic configuration of 1s² 2s² 2p². The 2p orbitals can effectively overlap to form pπ-pπ bonds, allowing carbon to form double (as in ethylene, C2H4) and triple bonds (as in acetylene, C2H2).

5. **Evaluate Silicon, Germanium, and Tin**:
- **Silicon (Si)**: Larger than carbon, it can form some pπ-pπ bonds, but they are weaker due to increased distance.
- **Germanium (Ge)**: Even larger than silicon, making effective pπ-pπ bonding less likely.
- **Tin (Sn)**: The largest of the group, with even weaker pπ-pπ bonding capabilities.

6. **Conclusion**: Among the four elements, carbon is the only one that can form strong double or triple bonds involving pπ-pπ bonding due to its small size and effective overlap of its p orbitals.

### Final Answer:
The element that forms double or triple bonds involving pπ-pπ bonding is **carbon (C)**.

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