Which of the following molecule is nonpolar?
(i) `PbCl_4` (ii) `BF_3`
(iii) `SnCl_2` (iv) `CS_2`

Options

A. (i), (ii), (iii)
B. (i), (ii), (iii), (iv)
C. (i), (ii), (iv)
D. (ii), (iii), (iv)

Explanation

To determine which of the given molecules is nonpolar, we will analyze the molecular geometry and the symmetry of each molecule. The molecules in question are:

1. \( \text{PbCl}_4 \)
2. \( \text{BF}_3 \)
3. \( \text{SnCl}_2 \)
4. \( \text{CS}_2 \)

### Step-by-Step Solution:

**Step 1: Analyze \( \text{PbCl}_4 \)**
- **Molecular Geometry**: \( \text{PbCl}_4 \) has a tetrahedral shape.
- **Symmetry**: The molecule is symmetrical because the four chlorine atoms are arranged evenly around the lead atom.
- **Polarity**: The dipole moments of the \( \text{Pb-Cl} \) bonds cancel each other out due to symmetry. Therefore, \( \text{PbCl}_4 \) is nonpolar.

**Step 2: Analyze \( \text{BF}_3 \)**
- **Molecular Geometry**: \( \text{BF}_3 \) has a trigonal planar shape.
- **Symmetry**: The three fluorine atoms are symmetrically arranged around the boron atom at 120-degree angles.
- **Polarity**: Similar to \( \text{PbCl}_4 \), the dipole moments of the \( \text{B-F} \) bonds cancel each other out. Thus, \( \text{BF}_3 \) is also nonpolar.

**Step 3: Analyze \( \text{SnCl}_2 \)**
- **Molecular Geometry**: \( \text{SnCl}_2 \) has a bent shape due to the presence of a lone pair on the tin atom.
- **Symmetry**: The molecule is not symmetrical because the lone pair creates an uneven distribution of charge.
- **Polarity**: The dipole moments of the \( \text{Sn-Cl} \) bonds do not cancel out, resulting in a net dipole moment. Therefore, \( \text{SnCl}_2 \) is polar.

**Step 4: Analyze \( \text{CS}_2 \)**
- **Molecular Geometry**: \( \text{CS}_2 \) has a linear shape.
- **Symmetry**: The two sulfur atoms are symmetrically arranged around the carbon atom.
- **Polarity**: The dipole moments of the \( \text{C-S} \) bonds cancel each other out due to symmetry. Thus, \( \text{CS}_2 \) is nonpolar.

### Conclusion:
The nonpolar molecules from the given options are:
- \( \text{PbCl}_4 \)
- \( \text{BF}_3 \)
- \( \text{CS}_2 \)

### Final Answer:
The nonpolar molecules are \( \text{PbCl}_4 \), \( \text{BF}_3 \), and \( \text{CS}_2 \).

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