Identify the incorrect statement among the following.

Options

A. 4f and 5f orbitals are equally shielded.
B. d-Block elements show irregular and erratic chemical properties among themselves.
C. La and Lu have partially filled d-orbitals and no other partially filled orbitals.
D. The chemistry of various lanthanoids is very similar.

Explanation

To identify the incorrect statement among the given options, we will analyze each statement step by step.

### Step 1: Analyze Statement 1
**Statement:** 4f and 5f orbitals are equally shielded.

- **Explanation:** The 4f and 5f orbitals belong to the lanthanide and actinide series, respectively. The shielding effect is influenced by the number of electrons in the orbitals and their spatial distribution. In general, 4f orbitals are more effective at shielding than 5f orbitals due to their proximity to the nucleus and their shape.
- **Conclusion:** This statement is incorrect because the 4f and 5f orbitals are not equally shielded, leading to different oxidation states for lanthanides and actinides.

### Step 2: Analyze Statement 2
**Statement:** The d-block elements show irregular and electrochemical properties among themselves.

- **Explanation:** D-block elements, also known as transition metals, exhibit variable oxidation states due to the involvement of d electrons in bonding. This variability leads to irregularities in their chemical and electrochemical properties.
- **Conclusion:** This statement is correct.

### Step 3: Analyze Statement 3
**Statement:** La and Lu have partially filled d-orbitals.

- **Explanation:** Lanthanum (La) has the electronic configuration of [Xe] 6s², meaning it does not have a partially filled d-orbital. Lutetium (Lu) has the configuration [Xe] 4f¹⁴ 5d¹ 6s², which means it has a partially filled d-orbital (5d).
- **Conclusion:** This statement is incorrect because La does not have a partially filled d-orbital, while Lu does.

### Step 4: Analyze Statement 4
**Statement:** The chemistry of various lanthanides is very similar.

- **Explanation:** The lanthanides have similar chemical properties due to the filling of the 4f orbitals, which leads to similar ionic sizes and charges. This similarity makes their separation difficult.
- **Conclusion:** This statement is correct.

### Final Conclusion
After analyzing all statements, we find that Statement 1 is incorrect regarding the shielding of 4f and 5f orbitals.

### Summary of Incorrect Statement:
- **Incorrect Statement:** 4f and 5f orbitals are equally shielded.

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