What is the fundamental difference in the electronic configurations between the group 1 and group 2 elements ? (b) On the basis of electronic configuration, how will you identify? (i) Chemically similar elements? The first element of a period?

• Group 1 elements have 1 valence electron in their atoms whereas group 2 elements have 2 valence electrons in their atoms. Eg: Lithium, sodium on group 1 have valency 1, Beryllium and magnesium have valency 2 belongs to group 2.

(b)(b) (i) All the chemically similar elements will have same valence electrons.

(ii) The 1st element of every period has 1 valence electron. Thus it is determined by the number of valence electrons in its atom.