Question

Calcium is an element with atomic number 20. Stating reason answer each of the following questions:
(i) Is calcium a metal or 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.

Answer 1

(i) Calcium is a metal since it has two electrons in its outermost shell which it can lose easily.
(ii) K(19) is placed before Ca(20) in the same period (fourth period). Since the atomic radius decreases along a period, the atomic radius of calcium is smaller than that. of potassium.
(iii) The formula of oxide of calcium is CaO, because the valency of calcium as well as that of oxygen is 2.