SCIENCE PHOTO LIBRARY SCIENCE PHOTO LIBRARY
Flame test sequence. Montage of a series of positive results of flame tests for various metal elements. The colours are due to the excitation of electrons in the metals by the heat of the flame. As these electrons lose their energy, they emit photons of light. The colour of the flame is different for different elements and can be used to identify unknown substances. The ones shown here are (left to right): barium (pale green), strontium (red), lithium (red), sodium (yellow), copper (green), and potassium (lilac).
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