Consider the following species, `1.0_(2)^(2-),2.Co^(+),3.O_(2)^(+)` Among these , sigma bond alone is present in

Options

A. 1 alone
B. 2 alone
C. 3 alone
D. 1 and 2

Answer

To determine which of the given species contains only sigma bonds, we will analyze each species one by one based on their molecular orbital configurations.

### Step 1: Analyze O₂²⁻ (Oxygen Dioxide Ion)
1. **Count the Electrons**: O₂ has 8 electrons (4 from each O atom), and since it has a -2 charge, we add 2 more electrons. Thus, O₂²⁻ has a total of 10 electrons.
2. **Molecular Orbital Filling**: The molecular orbital configuration for O₂²⁻ is:
- σ1s², σ*1s², σ2s², σ*2s², σ2p_z², π2p_x², π2p_y²
3. **Bonding and Antibonding Electrons**:
- Bonding: 10 (σ1s, σ2s, σ2p_z, π2p_x, π2p_y)
- Antibonding: 4 (σ*1s, σ*2s)
4. **Sigma Bonds**: O₂²⁻ has one sigma bond from σ2p_z.

### Step 2: Analyze CO⁺ (Carbon Monoxide Cation)
1. **Count the Electrons**: CO has 10 electrons (6 from C and 4 from O). Since it has a +1 charge, we remove 1 electron. Thus, CO⁺ has a total of 9 electrons.
2. **Molecular Orbital Filling**: The molecular orbital configuration for CO⁺ is:
- σ1s², σ*1s², σ2s², σ*2s², σ2p_z², π2p_x², π2p_y¹
3. **Bonding and Antibonding Electrons**:
- Bonding: 9 (σ1s, σ2s, σ2p_z, π2p_x)
- Antibonding: 4 (σ*1s, σ*2s, π2p_y)
4. **Sigma Bonds**: CO⁺ has one sigma bond from σ2p_z.

### Step 3: Analyze O₂⁺ (Oxygen Monoxide Cation)
1. **Count the Electrons**: O₂ has 16 electrons (8 from each O atom). Since it has a +1 charge, we remove 1 electron. Thus, O₂⁺ has a total of 15 electrons.
2. **Molecular Orbital Filling**: The molecular orbital configuration for O₂⁺ is:
- σ1s², σ*1s², σ2s², σ*2s², σ2p_z², π2p_x², π2p_y¹
3. **Bonding and Antibonding Electrons**:
- Bonding: 11 (σ1s, σ2s, σ2p_z, π2p_x)
- Antibonding: 4 (σ*1s, σ*2s, π2p_y)
4. **Sigma Bonds**: O₂⁺ has one sigma bond from σ2p_z.

### Conclusion
- O₂²⁻ has one sigma bond.
- CO⁺ has one sigma bond.
- O₂⁺ has one sigma bond.

However, O₂²⁻ is the only species that contains only sigma bonds without any pi bonds. Therefore, the answer is:

**O₂²⁻ contains only sigma bonds.**