Spectroscopy & Science

The visible spectrum of light and emission line spectra of hydrogen, neon, and iron. Note that the heavier an element is, the more spectral bands it has.

The spectrum of each chemical element is unique, like the fingerprint of a person. Each color spectral band of an element represents a particular wavelength of light. Spectral bands occur when an electron moves between two energy levels in an atom and emits energy as a photon (a particle of light). Measuring the strength and width of spectral lines allows the composition and physical properties of a substance to be determined. Spectral lines are designated according to the level of ionization by adding a Roman numeral to the symbol of the chemical element. Neutral atoms are denoted by I, singly ionized atoms (those missing one electron) with II, and so on. For example, Fe IX represents an iron atom that is missing eight electrons.