Atomic emission spectrum

An atomic emission spectrum is the set of discrete wavelengths emitted when excited atoms transition to lower-energy states. Its line pattern is characteristic of the element.

Electron transition: A change in an electron's energy state, often accompanied by absorption or emission of a photon. An emitted line corresponds to a transition from a higher atomic state to a lower one.
Quantum mechanics: The physical theory describing matter and radiation at atomic and subatomic scales. Its quantized states account for the discrete rather than continuous atomic spectrum.
Atomic emission spectroscopy: An analytical technique that identifies and measures elements from light emitted by excited atoms. It turns characteristic emission patterns into measurements of elemental composition.
Atomic absorption spectrum: The pattern of wavelengths selectively absorbed by atoms from incident radiation. Absorption lines arise when atoms gain energy, rather than release it as emission lines do.
Photon: A quantum of electromagnetic radiation that carries energy and momentum. The energy of each emitted photon matches the gap between the atom's states.
Atomic orbital: A quantum state describing the spatial distribution and properties of an electron in an atom. Orbital states help determine atomic energy levels and allowed transitions.
Flame test: A qualitative test that identifies some metal ions by the colors they produce in a flame. Flame colors arise from visible atomic emission lines excited by heat.
Continuous spectrum: A spectrum containing an unbroken range of wavelengths across a specified interval. A continuous spectrum contrasts with the separated wavelengths characteristic of atomic emission.
Atomic energy level: A discrete allowed energy state of an atom, associated with its electrons and nucleus. The spacing of these states determines which emission wavelengths are possible.
Wavelength: The spatial period of a wave, measured between corresponding points in successive cycles. Emission spectra identify radiation by its measured wavelengths.

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