(a) Atomic numbers of Mg and Al are 12 and 13 respectively. Write their electronic configuration.
(b) Mention the period of the Modern Periodic Table to which the above two elements belong. Give reason for your answer.

Explanation

(a) The electronic configuration of the elements are Mg(Z = 12) 2, 8, 2 , Al (Z = 13) 2, 8, 3.
(b) Both these elements belong to third period since their atoms have three shells.