The atomic number of K and Ca is 19 and 20 respectively and they belong to the same period
(a) Which amongst them would have smaller atomic size ?
(b) Which one would be more electropositive ?
© To which group would each of them belong ?
(a) Ca, as size decreases in a period due to an increase in the effective nuclear charge.
(b) K, as electropositive character decreases in a period due to an increase in the effective nuclear charge.
© K belongs to group 1 (Alkali Metals). Ca belongs to group 2 (Alkaline Earth Metals).