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Flame Test

A flame test is a common analytic procedure that can be used to distinguish different metal ions depending on the emission spectrum that is produced when the element is introduced into a hot flame. When a metal ion solution is held into a flame, heat will excite the valence electrons that emit a certain wavelength (λ) in the visible light spectrum when falling back to their original state (Figure 1). Most metal ions, therefore, have a characteristic and known flame color when applied to a flame test.

Simple graphic representation of atomic excitation and de-excitation. Atom is presented as black dot - the centre - with two black rings surrounding it - electron shells, with one electron at the inner shell. Upon receiving the energy beam, shown by equation - E equals hc divided by lambda, the atomic excitation takes place, and electron moves to the outer shell, and the inner shell changes colour to red. This excited electron emits an energy beam to the surroundings, called atomic de-excitation, and goes back to the inner shell, which changed colour from red to black again.

Figure 1: Electrons being excited and falling back while emitting light of a certain wavelength (λ) in the flame test.