chemistry

LANTHANIDE CONTRACTION

In inner transition elements the differentiating electron enters into ‘f’ orbitals of the antepenultimate shell.

As the atomic number increases in lanthanides due to the dispersed shape of f-orbitals and their poor shielding effect the atomic and ionic radii steadily decrease. This is called lanthanide contraction.

Lanthanide contraction is also observed in 5d transition series.

The atomic radius of 5d transition elements are very close to those of 4d transition elements due to Lanthanide contraction.

As a result 4d and 5d transition elements are more similar in properties when compared to 3d and 4d transition elements e.g. Zr and Hf resemble most closed to each other than other elements.