Which of the following molecular orbitals has two nodal planes ?

Options

A. `sigma 2s`
B. `pi 2p _(y)`
C. `pi ^(**)2p_(y)`
D. `sigma^(**)2p_(z)`

Answer

To determine which molecular orbital has two nodal planes, we will analyze the molecular orbitals mentioned in the question step by step.

### Step 1: Understanding Molecular Orbitals
Molecular orbitals are formed by the combination of atomic orbitals. They can be bonding or antibonding. Bonding orbitals have constructive interference, while antibonding orbitals have destructive interference.

**Hint:** Remember that bonding orbitals have no nodal planes, while antibonding orbitals can have nodal planes.

### Step 2: Analyze Sigma 2s Orbital
The sigma 2s orbital is a bonding molecular orbital formed by the constructive interference of two 2s atomic orbitals.

- **Characteristics:**
- It has a spherical shape.
- **Nodal Planes:** There are no nodal planes in sigma 2s.

**Hint:** Bonding orbitals like sigma 2s typically do not have nodal planes.

### Step 3: Analyze Pi 2px Orbital
The pi 2px orbital is formed by the lateral overlapping of p orbitals.

- **Characteristics:**
- It has a dumbbell shape.
- **Nodal Planes:** There is one nodal plane that passes through the nucleus, where the electron density is zero.

**Hint:** Pi orbitals usually have one nodal plane.

### Step 4: Analyze Pi* 2py Orbital
The pi* 2py orbital is an antibonding molecular orbital formed by the lateral overlapping of p orbitals with destructive interference.

- **Characteristics:**
- It has a similar dumbbell shape as pi orbitals.
- **Nodal Planes:** It has two nodal planes that are perpendicular to each other.

**Hint:** Antibonding pi orbitals can have multiple nodal planes, and they can be perpendicular.

### Step 5: Analyze Sigma* 2pz Orbital
The sigma* 2pz orbital is an antibonding molecular orbital formed by head-on overlap of p orbitals.

- **Characteristics:**
- It has a cylindrical shape.
- **Nodal Planes:** It has one nodal plane that bisects the orbital.

**Hint:** Sigma antibonding orbitals typically have one nodal plane.

### Conclusion
From the analysis:

- **Sigma 2s**: No nodal planes.
- **Pi 2px**: One nodal plane.
- **Pi* 2py**: Two nodal planes (perpendicular to each other).
- **Sigma* 2pz**: One nodal plane.

Thus, the molecular orbital that has two nodal planes is **Pi* 2py**.

### Final Answer
**The molecular orbital that has two nodal planes is Pi* 2py.**