Question

Why alkali metals imparts colour to the flame ?

Answer 1

When an alkali metal or its salt (especially chloride due to its more volatile nature) is heated in a burner flame, the electrons in the valence shell get excited and jump to higher energy level by absorbing energy. When the excited electron drops back to its ground state, the emitted radiation falls in the visible region and as a result, alkali metal or its salt impart colour to the flame. A list of alkali metals and the colour that they impart in flame is given below -

    Metal                          Colour of Flame

 Lithium (Li)                              Crimson

  Sodium (Na)                            Golden Yellow

  Potassium (K)                          Violet

  Rubidium (Rb)                         Red Violet

  Cesium (Cs)                             Blue

Answer 2

Alkali metals impart colour to the flame due to valence electrons

Explanation:

• The ionisation energy of alkali metal is very low.

• Valence electrons of alkali metal absorb the energy

• These energies are emitted from the flame and excited to higher levels.

• When excited electrons return to the ground state the absorbed energy is emitted in the form of light.
• The excited state is unstable compared to the ground state.
• So the electron will emit energy and return back to the ground state.