2.7.1f: recall the characteristic flame colours formed by group 1 and 2 compounds and explain their origin in terms of electron transitions

THE HYDROGEN SPECTRUM

As a substance is heated up, its electrons are excited into higher energy levels

• as the electrons lose energy, they fall back down, and light in certain wavelengths is emitted

METHOD

1. dip a nichrome or platinum wire (chemically inert) into hydrochloric acid (cleans impurities and chloride ions create a more visible colour change)
2. dip the damp nichrome or platinum wire into a solid sample of the metal
3. hold the metal in a non-luminous Bunsen flame and observe a colour change

COLOUR CHANGES

Sodium = yellow

Potassium = lilac

Calcium = yellow-red

Lithium or strontium = red

Barium = pale/apple green