Question

The UV-visible absorption bands in the spectra of lanthanoid ions are ‘X’, probably because of the excitation of electrons involving ‘Y’. The ‘X’ and ‘Y’, respectively, are :

• A. Broad and f orbitals
• B. Narrow and f orbitals
• C. Broad and d and f orbitals
• D. Narrow and d and f orbitals

Answer 1

The Correct Option is B

To determine the correct answer to the given question, we need to understand the nature of the UV-visible absorption bands in lanthanoid ions and the orbitals involved in these electronic transitions.

1. Understanding Lanthanoid Ions and Electronic Transitions:

• Lanthanoids are a series of 15 metallic elements from lanthanum (La) to lutetium (Lu) in the periodic table.
• These elements have partially filled 4f orbitals, and the electronic transitions occur within these f orbitals.

2. Nature of Absorption Bands:

• The electronic transitions involving f orbitals in lanthanoid ions result in absorption bands that are typically narrow.
• This narrowness is due to the shielding effect of the outer electrons that prevents the f electrons from interacting significantly with the surrounding environment.

Explanation of Options:

• The option B: Narrow and f orbitals is the correct answer because the UV-visible absorption bands are narrow due to the localized nature of f orbital transitions.
• Other options refer to d orbitals, which are not primarily involved in absorption bands for lanthanoids. Additionally, 'broad' absorption bands are not characteristic of f orbital transitions.

Conclusion:

The correct choice is: Narrow and f orbitals because the UV-visible absorption bands in lanthanoid ions are narrow due to f-f transitions.