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Chemistry LibreTexts

History & Theory

Atomic spectroscopy began with the realization in the mid-19th century that salts in a flame could emit light of wavelength specific to metallic elements introduced to the flame as powders or solutions, and that light of the same wavelength might be missing from emission from stars (including the sun) because the elements absorbed light. The figure illustrates that sodium emits light at 588.9 nm and 589.5 nm (if the atoms are hot enough), or absorbs light if the atoms are cold. "Hot" and "cold" are vague, and the way to know what wavelengths correspond to which elements aren't obvious. We discuss this later.