Which of the following species contain only sigma bond?

Options

A. `SiCl_4`
B. NO_3^-
C. HNC
D. `SO_3^(2-) `

Answer

To determine which of the given species contains only sigma bonds, we need to analyze the bonding in each species.

### Step-by-Step Solution:

1. **Identify the species**: We need to check the bonding in the following species:
- Silicon tetrachloride (SiCl₄)
- Nitrate ion (NO₃⁻)
- HNC (Hydrogen isocyanide)
- Sulfite ion (SO₃²⁻)

2. **Analyze SiCl₄**:
- Silicon (Si) has 4 valence electrons and forms 4 single bonds with 4 chlorine (Cl) atoms.
- Each Si-Cl bond is a sigma bond.
- Therefore, SiCl₄ contains only sigma bonds.

3. **Analyze NO₃⁻**:
- In the nitrate ion, nitrogen (N) is bonded to three oxygen (O) atoms.
- The bonding includes one double bond (which consists of one sigma bond and one pi bond) and two single bonds.
- Since there is a pi bond present, NO₃⁻ does not contain only sigma bonds.

4. **Analyze HNC**:
- In HNC, nitrogen (N) forms a triple bond with carbon (C).
- A triple bond consists of one sigma bond and two pi bonds.
- Therefore, HNC does not contain only sigma bonds.

5. **Analyze SO₃²⁻**:
- In the sulfite ion, sulfur (S) is bonded to three oxygen (O) atoms.
- The structure includes one double bond (which has one sigma and one pi bond) and one single bond.
- Thus, SO₃²⁻ does not contain only sigma bonds.

6. **Conclusion**:
- Among the species analyzed, only SiCl₄ contains only sigma bonds.

### Final Answer:
The species that contains only sigma bonds is **SiCl₄**.

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