What is lanthanide contraction? Write any two of its consequences.

Explanation

Lanthanide contraction The overall decrease in atomic and ionic radii from lanthanum to lutetium , due to the imperfect shielding one electron by another in the same subshell , is known as lanthanide contraction . The decrease in atomic radii is not quite regular as it is regular in `M^(3+)` ions .
(a) Similar physical and chemical properties among lanthanide .
(ii) Elements of second and third d- series exhibit similar radii (e.g . Zr -160 pm , Hf - 159 pm) and have very similar physical and chemical properties .