Question

Reason of lanthanoid contraction is:

• A. negligible screening effect of f orbitals.
• B. increasing nuclear charge.
• C. decreasing nuclear charge.
• D. decreasing screening effect.

Answer 1

The correct option is A negligible screening effect of f orbitals.

Reason of lanthanoid contraction is Negligible screening effect of f orbitals. hence, as the nuclear charge increases, the valence shell is pulled slightly towards nucleus. Thus the size of tripositive ion decreases with increase in the atomic number. This decrease is very small and u is known as lanthanide contraction.

Hence, the correct option is $A$.