Question

Which of the following factor may be regarded as the main cause of Lanthanide contraction?

• A. Poor shielding of 4 f-electrons in compare to other electrons in the sub-shell.
• B. Effective shielding of one of the 4 f-electrons by another in the sub-shell.
• C. Poorer shielding of 5 d electron by 4 f- electrons.
• D. Greater shielding of 5 d electron by 4 f- electron.

Answer 1

Answer: (A)

Poor shielding of 4 f-electrons in compare to other electrons in the sub-shell.

Answer 2

This phenomenon is associated with the intervention of the 4f orbitals which must be filled before the 5d series of elements begin. The filling of 4f before 5d orbital results in a regular decrease in atomic radii called

Lanthanoid contraction. This is because of poor shielding of one of the 4 f-electrons by another in the sub-shell.