Which of the followig is/are correct regarding the magnitude of crystal field splitting energy `Delta`?

Options

A. it depends on the coordination geometry. `Delta` for octahedral `gt` square planar `gt` tetrahedral
B. it depends on oxidation number of central atom `M.Delta` for `M^(3+)gtM^(2+)`
C. it depends on whether the central atom M belongs to 3 series or `4d//5d` series.
D. it depedns on the ligand.

Explanation

To determine which statements regarding the magnitude of crystal field splitting energy (Δ) are correct, we will analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** "Delta for octahedral is greater than Delta for square planar which is greater than Delta tetrahedral."

**Analysis:** This statement is incorrect. The correct order of crystal field splitting energy is:
- Δ (square planar) > Δ (octahedral) > Δ (tetrahedral).
Square planar complexes typically have the highest splitting energy due to the arrangement of ligands and the resulting electron repulsion.

**Conclusion:** This statement is **incorrect**.

### Step 2: Analyze the second statement
**Statement:** "Delta depends on the oxidation number of central metal M. Delta for M3+ is greater than M2+."

**Analysis:** This statement is correct. Higher oxidation states of the metal ion (like M3+) lead to a greater effective nuclear charge, which increases the splitting of d-orbitals due to stronger interactions with the ligands. Therefore, Δ for M3+ is indeed greater than Δ for M2+.

**Conclusion:** This statement is **correct**.

### Step 3: Analyze the third statement
**Statement:** "Delta depends on whether the central atom M belongs to 3d series or 4d or 5d series."

**Analysis:** This statement is also correct. The crystal field splitting energy is influenced by the type of metal ion. For 4d and 5d series, the ligands tend to act as stronger field ligands compared to 3d series, resulting in larger Δ values.

**Conclusion:** This statement is **correct**.

### Step 4: Analyze the fourth statement
**Statement:** "Delta depends on the ligand."

**Analysis:** This statement is correct as well. The nature of the ligand significantly affects the crystal field splitting energy. Strong field ligands cause greater splitting and can lead to low-spin complexes, while weak field ligands result in smaller splitting and high-spin complexes.

**Conclusion:** This statement is **correct**.

### Final Conclusion
Based on the analysis:
- The first statement is **incorrect**.
- The second, third, and fourth statements are **correct**.

Thus, the answer is that the last three options regarding the magnitude of crystal field splitting energy Δ are correct.

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