Question

The property seen in f-block elements is:

• A. Lanthanoid contraction
• B. Actinide contraction
• C. Lanthanoid expansion
• D. (a) and (b) above

Answer 1

The correct option is D (a) and (b) above

The property seen in f-block elements are Lanthanoid contraction and Actinide contraction.
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.
The gradual decrease in the ionic radii with the increase in atomic number of actinoids is called actinoid contraction. It is due to the imperfect shielding of one 5f electrons by another in the same subshell. Along the series, the nuclear charge and number of 5f electrons increases by one unit.
Hence option (d) is correct.