Question

What does lanthanoid contraction mean?

Answer 1

Lanthanoid contraction:

• "With the successive filling of the inner orbitals, $4\mathrm{f}$, there is a gradual decrease in the atomic and ionic sizes of these metals along with the series that is known as lanthanoid contraction."
• “The two series of inner transition elements, lanthanoids, and actinoids shows Lanthanoid contraction.