write formula of sodium oxide and also write elements present in them.

Explanation

Lanthanoid contraction refers to the gradual decrease in the size of Lanthanoids and their trivalent ions `(Z = 58 "to" 71)` whereas actinoid contraction refers to the gradual decrease in the size of the actinoid or their ions `(M^(3+) or M^(4+)) (Z = 90" to "103)`.