According to V.B.T., atoms of element form bond only to pair up their unpaired electrons present in ground state or excited state. This pairing of unpaired electron will take place by overlapping of orbitals each one having one unpaired electron with opposite spin.
Which of the following orbital cannot form `delta`-bond ?

Options

A. `d_(x^(2)-y^(2))` orbital
B. `d_(xy)` orbital
C. `d_(z^(2))` orbital
D. `d_(zx)` orbital

Answer

To determine which orbital cannot form a delta bond according to Valence Bond Theory (VBT), we need to understand the characteristics of delta bonds and the orbitals involved.

### Step-by-Step Solution:

1. **Understanding Delta Bonds**: Delta bonds are formed by the mutual overlapping of four lobes of d-orbitals. For a delta bond to form, we need orbitals that have four lobes to overlap with another set of four lobes.

2. **Identifying the Orbitals**: The question provides four options of d-orbitals:
- A) \( d_{x^2 - y^2} \)
- B) \( d_{xy} \)
- C) \( d_{z^2} \)
- D) \( d_{zx} \)

3. **Analyzing Each Orbital**:
- **Option A: \( d_{x^2 - y^2} \)**: This orbital has four lobes oriented along the x and y axes. It can participate in delta bonding.
- **Option B: \( d_{xy} \)**: This orbital also has four lobes, positioned in the xy-plane. It can participate in delta bonding.
- **Option C: \( d_{z^2} \)**: This orbital has a different shape, consisting of two lobes along the z-axis and a ring around the equatorial plane. It does not have four lobes and therefore cannot form a delta bond.
- **Option D: \( d_{zx} \)**: This orbital has four lobes oriented in the zx-plane. It can participate in delta bonding.

4. **Conclusion**: Among the given options, the orbital that cannot form a delta bond is **Option C: \( d_{z^2} \)**, as it lacks the necessary four lobes for delta bonding.

### Final Answer:
**C) \( d_{z^2} \)** cannot form a delta bond.

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