Lanthanide contraction: Lanthanoid contraction refers to the

Lanthanoid contraction refers to the gradual decrease in the ionic radii of the lanthanide series elements (from lanthanum to lutetium) as we move from left to right across the series. This contraction occurs due to the ineffective shielding of the nuclear charge by the f-electrons. Learn about the atomic radius trend of the Lanthanide series and how it is caused by the poor shielding of the 4f electrons. Compare the Lanthanide Contraction with the D Block Contraction and see how it affects ionization energy and properties. 1) Definition of Lanthanoid Contraction : The Lanthanoid contraction may be defined as gradual (or small) the decrease in atomic and ionic radii of lanthanoids with the increase in atomic number.