. The electronic configuration of an element X is 2, 8, 8, 2
To which (a) period and (b) group of the modern periodic table does 'X' belong? State its valency. Justify your answer in each case.
Ans. Electronic configuration of 'X' is 2, 8, 8, 2.
(a) It belongs to the 4th period because it has four energy shells and period number of an element is equal to the number of energy shells.
(b) lt belongs to 2nd group because it has 2 valence electrons and the group number of an
element having upto two valence electrons is equal to the number of valence electrons. Its valency is '2'. To acquire inert gas
configuration 'X' either loses 2 electrons or gains 6 electrons. Since the shorter route is to lose 2 electrons for obtaining inert gas configuration, hence its valency is 2