Question

(a) What is the fundamental difference in the electron configurations between the group 1 and group 2 elements?

(b) On the basis of electronic configuration, how will you identify:
(i) chemically similar elements?
(ii) the first element of a period?

Answer 1

(a)

Group I	Electronic configuration	Group II	Electronic configuration
Li (Lithium)	2, 1	Be (Beryllium)	2,2
Na (Sodium)	2, 8, 1	Mg (Magnesium)	2,8,2
K (Potasium)	2, 8, 8, 1	Ca (Calcium)	2,8,8,2

(b) (i) Elements having the same number of valence electrons in their atoms will be chemically similar because the chemical properties of an element depend on the number of electrons present in the outermost shell (valence electrons) of an atom of the element.

(ii) The first element of each period has only one outermost electron. For example, if an element has an electronic configuration of (2,1), we understand that the element belongs to group 1.