Question

Which of the following elements give light green colour in flame test?
A.K
B.Rb
C.Ca
D.Ba

Answer 1

Flame test can be understood as a basic analytical procedure which is often implemented to determine the nature of the metal used in a given compound. Different elements often tend to give different coloured flames. The colour of the flames produced depend on the electronic configuration of the atoms of these elements.

Complete Step-by-Step Answer:
Before we move forward with the solution of the given question, let us first understand some important basic concepts.
When an atom is heated, the thermal energy is added directly to the valence electrons of the atom. These electrons hence move to a higher energy state till the point where the energy is supplied to the electrons, once these electrons return to their original energy state, the atoms emit energies of certain wavelengths which corresponds to the total number of electrons that are brought to the higher energy state.
Since each electron would have a capacity to emit a certain energy when brought to the ground state, a variation in the number of electrons would vary the amount of energy emitted and hence would vary the colour of the flame obtained. Let us now discuss the given options:
1.K
The electronic configuration of potassium is $[Ar]4{s^1}$ and the colour of its flame is Lilac
2.Rb
The electronic configuration of Rb is $[Kr]5{s^1}$ and the colour of its flame is Red - violet
3.Ca
The electronic configuration of Calcium is $[Ar]4{s^2}$ and the colour of its flame is Orange - red
4.Ba
The electronic configuration of Xenon is $[Xe]6{s^2}$ and the colour of its flame is Green

Hence, Option D is the correct option

Note: There are certain metals that have the same colour of the flame. One such example is white flame. A variety of elements including Titanium, Magnesium, Beryllium, Aluminium, Chromium, Cobalt, Nickel burn in air with a white flame.