A: All square planar complexes can exhibit geometrical isomerism.
R: In square planar complexes metal assumes `sp^(3)` hybridisation.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the question, we need to analyze both the assertion and the reason provided:

### Step 1: Analyze the Assertion
The assertion states: "All square planar complexes can exhibit geometrical isomerism."

- **Geometrical Isomerism**: This type of isomerism occurs when compounds have the same formula but different spatial arrangements of atoms.
- **Square Planar Complexes**: Square planar complexes can exhibit geometrical isomerism, but not all square planar complexes do.
- **Types of Square Planar Complexes**:
- Complexes of the type M-A2-B2 (where M is bonded to two A ligands and two B ligands) can exhibit geometrical isomerism.
- Complexes of the type M-A-B-C-D (where M is bonded to four different ligands) can also exhibit geometrical isomerism.
- However, complexes of the type M-A4 (four identical ligands) or M-A3B (three identical ligands and one different) do not exhibit geometrical isomerism.

Thus, the assertion is **false** because not all square planar complexes exhibit geometrical isomerism.

### Step 2: Analyze the Reason
The reason states: "In square planar complexes, metal assumes sp³ hybridization."

- **Hybridization in Square Planar Complexes**: The correct hybridization for square planar complexes is **dsp²**, not sp³.
- **sp³ Hybridization**: This hybridization leads to a tetrahedral geometry, which is not applicable to square planar complexes.

Thus, the reason is also **false**.

### Conclusion
Both the assertion and the reason are false. Therefore, the correct answer is option 4: "Both assertion and reason are false."

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