Which of the following `MO` s have one nodal plane ? .

Options

A. `sigma 1s`
B. `sigma^(**) 1s`
C. `sigma 2p_(z)`
D. `sigma^(**)2p_(z)`

Explanation

To determine which molecular orbitals (MOs) have one nodal plane, we will analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Analyze Sigma 1s Molecular Orbital (σ 1s)**:
- The σ 1s molecular orbital is formed by the constructive interference of two 1s atomic orbitals.
- Since it is formed by constructive interference, there are no nodal planes present in this molecular orbital.
- **Conclusion**: σ 1s has **0 nodal planes**.

2. **Analyze Sigma Star 1s Molecular Orbital (σ* 1s)**:
- The σ* 1s molecular orbital is formed by the destructive interference of two 1s atomic orbitals.
- This type of interference creates a nodal plane between the two nuclei.
- **Conclusion**: σ* 1s has **1 nodal plane**.

3. **Analyze Sigma 2pz Molecular Orbital (σ 2pz)**:
- The σ 2pz molecular orbital is formed by the constructive interference of two 2pz atomic orbitals.
- Similar to σ 1s, this type of interference does not create any nodal planes.
- **Conclusion**: σ 2pz has **0 nodal planes**.

4. **Analyze Sigma Star 2pz Molecular Orbital (σ* 2pz)**:
- The σ* 2pz molecular orbital is formed by the destructive interference of two 2pz atomic orbitals.
- This results in the formation of a nodal plane between the two nuclei.
- **Conclusion**: σ* 2pz has **1 nodal plane**.

### Final Answer:
The molecular orbitals that have one nodal plane are **σ* 1s** and **σ* 2pz**.