The atomic numbers of three elements are given below:
Element (symbol) - A - B - C
Atomic number - 3 - 6 - 9
Write the symbol of the element which belongs to (a) group 1, (b) group 14, of the periodic table. State the period of the periodic table to which these elements belong. State reason to support your answer.
(a) A belongs to group 1.
(b) B belongs to group 14.
These elements belong to second period because these elements have two shells. A has electronic configuration 2, 1 and has one valence electron so, belongs to group 1. ‘B’ has electronic configuration 2, 4 and has four valence electrons so, belongs to group 14 and period 2. ‘C’ has electronic configuration 2, 7 and has one valence electron. All of them contain two shells and so belong to second period.