Question

Elements of $1A$ group give colour in bunsen burner flame because of:
A. low ionization potential
B. low melting point
C. softness
D. None of the above.

Answer 1

In order to answer this question, you must be aware of the properties of the Elements of $1A$ group. Recall and enlist the properties of colour when elements of $1A$ group are burned. Choose the most appropriate answer by going through all the properties carefully.

Complete step-by-step answer: Elements present in ${1^{st}}$ group of the periodic table are the alkali metals: hydrogen $(H)$ , lithium $(Li)$ , sodium $(Na)$ , potassium $(K)$ , rubidium $(Rb)$ , cesium $(Cs)$ , and francium $(Fr)$ . These metals are (except hydrogen) very soft, shiny, low-melting point , highly reactive metals, which tarnish when reacting with air.
Step 1: In this step we will enlist the reason that why alkali metals gives the flame test:
Alkali metals show characteristic colours on the fire due to low ionisation enthalpy, when these alkali metal or salt of it is heated in a flame, the valence electrons are excited and go in the higher energy level.
When these excited electrons return to the ground state, the absorbed energy is emitted in the visible region of the electromagnetic spectrum and hence the flame appears to be coloured.
Clearly, we conclude that alkali metals give flame test by a specific color since alkali metals have minimum ionization potential so when they are heated electrons go from lower energy level to higher level and then fall back by releasing light energy in the form of photon.
And hence we got our answer.

Clearly, the correct answer is Option A.

Note: A flame test is a process used in chemistry to confirm the presence of certain elements, primarily metal ions, based on each element's characteristic emission spectrum. The color of flames also depends on temperature.