A: Lanthanoids have +3 as most common oxidation state.
B: Electrons of 4f in lanthanoids rarely participate

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. Statement A is true ,Statement B is false

Answer

**Step-by-Step Solution:**

1. **Understanding Lanthanides**: Lanthanides are a series of 15 elements from cerium (Ce) to lutetium (Lu) in the periodic table. They are known for their unique electronic configurations and properties.

2. **Common Oxidation State**: The most common oxidation state of lanthanides is +3. This is primarily due to the electronic structure of these elements.

3. **Role of 4f Electrons**: The 4f electrons in lanthanides are shielded by the 6s and 5d orbitals. This shielding effect makes it difficult for the 4f electrons to be removed or to participate in bonding.

4. **Electron Removal**: When considering the removal of electrons to achieve the +3 oxidation state, typically, two electrons are removed from the 6s orbital, and one electron is removed from the 4f orbital. This results in a total of three electrons being removed, leading to the +3 oxidation state.

5. **Conclusion**: Therefore, the statement that lanthanides have +3 as the most common oxidation state is correct. Additionally, the assertion that the 4f electrons rarely participate in bonding due to being shielded by the 6s and 5d orbitals is also accurate.

**Final Answer**: Both statements A and B are correct regarding lanthanides.

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