In which of the following molecules, central atom is not `sp^3` hybridized?

Options

A. `NH_3`
B. `CH_4`
C. H_2O
D. `CO_2`

Answer

To determine which of the given molecules has a central atom that is not sp³ hybridized, we will analyze each molecule one by one, focusing on the central atom's hybridization.

### Step-by-Step Solution

1. **Identify the Molecules**: The molecules given are:
- Ammonia (NH₃)
- Methane (CH₄)
- Water (H₂O)
- Carbon Dioxide (CO₂)

2. **Determine the Hybridization of Each Molecule**:
- **Ammonia (NH₃)**:
- Nitrogen (N) has 5 valence electrons.
- It forms 3 sigma bonds with hydrogen atoms and has 1 lone pair.
- Hybridization index = Number of sigma bonds + Number of lone pairs = 3 + 1 = 4.
- Therefore, NH₃ is **sp³ hybridized**.

- **Methane (CH₄)**:
- Carbon (C) has 4 valence electrons.
- It forms 4 sigma bonds with hydrogen atoms and has 0 lone pairs.
- Hybridization index = 4 + 0 = 4.
- Therefore, CH₄ is **sp³ hybridized**.

- **Water (H₂O)**:
- Oxygen (O) has 6 valence electrons.
- It forms 2 sigma bonds with hydrogen atoms and has 2 lone pairs.
- Hybridization index = 2 + 2 = 4.
- Therefore, H₂O is **sp³ hybridized**.

- **Carbon Dioxide (CO₂)**:
- Carbon (C) has 4 valence electrons.
- It forms 2 double bonds with oxygen atoms, which counts as 2 sigma bonds, and has 0 lone pairs.
- Hybridization index = 2 + 0 = 2.
- Therefore, CO₂ is **sp hybridized**.

3. **Conclusion**: Among the given molecules, only Carbon Dioxide (CO₂) has a central atom (carbon) that is not sp³ hybridized. It is sp hybridized.

### Final Answer:
The central atom that is not sp³ hybridized is in **Carbon Dioxide (CO₂)**.

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