Flame Test
A qualitative test in which a sample is heated in a flame and identified by the characteristic colour emitted.
Unit
nm
In depth
Thermal energy excites valence electrons, which emit light of definite wavelength as they fall back to lower levels. The test is quick and needs no equipment, but colours can be masked by the intense yellow of trace sodium, which cobalt blue glass is used to filter out.
Examples in the real world
Lithium crimson, sodium yellow, potassium lilac, calcium brick red, copper blue-green and barium apple green.