Question

Lanthanide contraction is due to increase in:

• A. shielding by 4f electrons
• B. atomic number
• C. effective nuclear charge
• D. size of 4 f-orbital

Answer 1

The correct option is C effective nuclear charge

Lanthanoid contraction effect results from poor shielding of nuclear charge (nuclear attractive force on electrons) by 4f electrons so effective nuclear charge increases; the 6s electrons are drawn towards the nucleus, thus resulting in a smaller atomic radius.