Question
Calcium is an element with atomic number 20. Stating reason, answer each of the following questions:-
(i) Is calcium a metal or a non-metal?
(ii) Will its atomic radius be larger or smaller than that of potassium with atomic number 19?
(iii) Write the formula of its oxide.
Solution
(a) The atomic number of calcium is 20. Its electronic configuration is 2, 8, 8, 2. The valency of calcium is 2; therefore, it is a metal belonging to the group 2 of the periodic table.
(b) Atomic numbers of potassium and calcium are 19 and 20, respectively. Both the elements lie in the third period of the periodic table. Potassium lies to the left of calcium in the period. We know that on moving left to right across a period, the atomic radius of the atom decreases. This happens because of the increase in the force of attraction by the nucleus on going left to right in the period.
(c) The oxide of calcium is calcium oxide and its chemical formula is CaO.
