Assuming z-axis to be intermolecular axis, designate the molecule orbitals from the following combination.
(i) 2px + 2px (ii) 2pz+2pz (iii) 2py-2py

Answer

To designate the molecular orbitals from the given combinations of atomic orbitals, we will analyze each combination step by step.

### Step 1: Analyze the combination 2px + 2px
1. **Identify the orbitals**: We have two 2px orbitals.
2. **Determine the orientation**: The z-axis is the intermolecular axis, which means the 2px orbitals will be oriented along the x-axis.
3. **Visualize the overlap**: The two 2px orbitals will overlap sidewise.
4. **Type of bond formed**: This sidewise overlap leads to the formation of a pi (π) bond.
5. **Designation of the molecular orbital**: Since the overlap is constructive, we denote this molecular orbital as π (bonding molecular orbital) formed from 2px.

### Step 2: Analyze the combination 2pz + 2pz
1. **Identify the orbitals**: We have two 2pz orbitals.
2. **Determine the orientation**: The z-axis is the intermolecular axis, so the 2pz orbitals will be aligned along the z-axis.
3. **Visualize the overlap**: The two 2pz orbitals will overlap end-to-end.
4. **Type of bond formed**: This end-to-end overlap leads to the formation of a sigma (σ) bond.
5. **Designation of the molecular orbital**: Since the overlap is constructive, we denote this molecular orbital as σ (bonding molecular orbital) formed from 2pz.

### Step 3: Analyze the combination 2py - 2py
1. **Identify the orbitals**: We have two 2py orbitals.
2. **Determine the orientation**: The z-axis is the intermolecular axis, and the 2py orbitals will be oriented along the y-axis.
3. **Visualize the overlap**: The two 2py orbitals will overlap sidewise, but since there is a negative sign, it indicates destructive interference.
4. **Type of bond formed**: This leads to the formation of an anti-bonding molecular orbital.
5. **Designation of the molecular orbital**: We denote this molecular orbital as π* (anti-bonding molecular orbital) formed from 2py.

### Summary of Designated Molecular Orbitals:
- For 2px + 2px: **π (bonding molecular orbital)**
- For 2pz + 2pz: **σ (bonding molecular orbital)**
- For 2py - 2py: **π* (anti-bonding molecular orbital)**

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