Question

Lanthanide contraction is caused due to _________.

• A. the same effective nuclear charge from Ce to Lu.
• B. the imperfect shielding on outer electrons by 4f electrons from the nuclear charge.
• C. the appreciable shielding on outer electrons by 4f electrons from the nuclear charge.
• D. the appreciable shielding on outer electrons by 5d electrons from the nuclear charge.

Answer 1

The correct option is B the imperfect shielding on outer electrons by 4f electrons from the nuclear charge.

Lanthanide contraction is a term used in chemistry to describe the greater-than-expected decrease in ionic radii of the elements in the lanthanide series from atomic number 57, lanthanum, to 71, lutetium, which results in smaller than otherwise expected ionic radii for the subsequent elements starting with 72, Hafnium.The effect results from poor shielding of nuclear charge (nuclear attractive force on electrons) by 4f electrons; the 6s electrons are drawn towards the nucleus, thus resulting in a smaller atomic radius.