Which of the following statement is not correct?

Options

A. `La(OH)_3` is less basic than `Lu(OH)_3`
B. In Lanthanide series ionic radius of `Ln^(+3)` ions decreases
C. La is actually an element of transition series rather Lanthanide
D. Aomic radius of Zr and Hf are same because of Lanthanide contraction

Answer

To solve the question, we need to evaluate the four statements provided and identify which one is incorrect. Let's analyze each statement step by step.

### Step 1: Analyze the Statements
1. **Statement 1**: La(OH)₃ is less basic than Lu(OH)₃.
2. **Statement 2**: In the lanthanide series, the ionic radius of Ln³⁺ ions decreases from La³⁺ to Lu³⁺.
3. **Statement 3**: La is actually an element of the transition series.
4. **Statement 4**: The atomic radius of zirconium and hafnium are the same because of lanthanide contraction.

### Step 2: Evaluate Each Statement
1. **Statement 1**: La(OH)₃ is less basic than Lu(OH)₃.
- This statement is **incorrect**. As we move from La to Lu in the lanthanide series, the ionic size decreases, leading to an increase in covalent character and a decrease in basicity. Therefore, La(OH)₃ is actually **more basic** than Lu(OH)₃.

2. **Statement 2**: In the lanthanide series, the ionic radius of Ln³⁺ ions decreases from La³⁺ to Lu³⁺.
- This statement is **correct**. The ionic radius of lanthanide ions decreases as we move from La³⁺ to Lu³⁺ due to the increasing nuclear charge which pulls the electrons closer to the nucleus.

3. **Statement 3**: La is actually an element of the transition series.
- This statement is **correct**. Lanthanum (La) is considered a transition metal and is often included in the f-block of the periodic table.

4. **Statement 4**: The atomic radius of zirconium and hafnium are the same because of lanthanide contraction.
- This statement is **correct**. The similarity in atomic radii of zirconium (Zr) and hafnium (Hf) is attributed to the lanthanide contraction, which affects the size of the elements in the d-block.

### Conclusion
The statement that is **not correct** is:
**La(OH)₃ is less basic than Lu(OH)₃.**

### Final Answer
**La(OH)₃ is less basic than Lu(OH)₃** is the incorrect statement.

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