Question

Potassium ions imparts _______ colour to the flame.
(a) Red
(b) Lilac
(c) Green
(d)Violet

Answer 1

Hint: Potassium itself is colourless or white in colour but when it is heated, it imparts a somewhat light pale or bluish colour to the flame due to excitation of the electrons to the higher energy orbitals and thus, their return to the original energy levels. Now identify the colour imparted.

Complete step by step answer:
Potassium is an alkali metal and it belongs to the category of the alkali metal and has the atomic number of 19 and mass number as 39. The outer shell electronic configuration of potassium is 4${{\text{s}} ^ {1}} $.
Being an alkali metal, it is very soft and can be easily cut with a knife. It is white in colour with silvery shine and it has a very low melting point too. Since it is an alkali metal, it is a very good conductor of heat and electricity and the ions when it gets charged helps to generate electricity.
When the potassium( alkali metal) is made to undergo the flame test, the loosely bound electrons which are present in the outermost valence shell of the potassium atom gets excited ,it gains energy and jumps to the higher energy levels and after some time when they return to their original energy level orbitals ,they emit radiations which when falls under the region of the visible light, it imparts colour to the flame and the colour imparted by the potassium ion is pale lilac colour i.e. Light blue colour to the flame.

So, option(b) is correct.

Note: Flame tests are used to identify the presence of metal ions in a compound as different metal ions imparts different colour to the flame and hence can be easily distinguishable through their colour.E.g. sodium ion imparts yellow colour to the flame, calcium ion imparts orange-red colour to the flame etc.