Question

Why are the elements 57 through 71 and 89 through 102, found separately at the bottom of the table?

Answer 1

Elements from 57 to 71 are Lanthanoids and from 89 to 103 are Actinoids. Simply I would say Actinoids have less similarity in chemical properties than Lanthanoids. On the other hands, Actinoids have randomized chemical strutural bonds.