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 solve the question of which element forms double or triple bonds involving p pi - p pi bonding, we can follow these steps:

### Step 1: Understand the Elements
The elements given in the question are carbon, silicon, germanium, and tin. All these elements belong to group 14 of the periodic table.

### Step 2: Analyze the Electronic Configurations
- **Carbon (C)**: Atomic number 6
- Electronic configuration: 1s² 2s² 2p²
- **Silicon (Si)**: Atomic number 14
- Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p²
- **Germanium (Ge)**: Atomic number 32
- Electronic configuration: [Ar] 3d¹⁰ 4s² 4p²
- **Tin (Sn)**: Atomic number 50
- Electronic configuration: [Kr] 4d¹⁰ 5s² 5p²

### Step 3: Identify the Bonding Types
- **p pi - p pi Bonding**: This type of bonding occurs when two p orbitals from different atoms overlap.
- **d pi - p pi Bonding**: This occurs when a d orbital overlaps with a p orbital.

### Step 4: Determine the Availability of d Orbitals
- **Carbon**: Has no d orbitals available (only has 2p orbitals).
- **Silicon**: Has d orbitals available but typically forms p pi - p pi bonds.
- **Germanium**: Has d orbitals available and can form d pi - p pi bonds.
- **Tin**: Also has d orbitals available and can form d pi - p pi bonds.

### Step 5: Conclusion
Since carbon is the only element that does not have vacant d orbitals, it can only form double or triple bonds through p pi - p pi bonding. Therefore, the answer to the question is:

**Answer: Carbon (C)**

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