Those elements impart colour to hte flame on heating in it, the atoms of which require low energy for the ionisation (i.e., absorb energy in the visible region of spectrum). The elements of which of the following groups will impart colour to the flame?

Answer

A, C

Explanation

(a,c) The elements of group 1 (alkali metals) and group 2 (alkaline earth metals) have 1 and 2 electrons respectively in their volume shells and hence have low ionisation energies. In other words, elements of group 1 and 2 imparts colour to the flame.