The range of characteristic frequencies of electromagnetic radiation that are readily absorbed and emitted by an atom. The atomic spectrum is an effect of the quantized orbits of electrons around the atom. An electron can jump from one fixed orbital to another: if the orbital it jumps to has a higher energy, the electron must absorb a photon of a certain frequency; if it is of a lower energy, it must give off a photon of a certain frequency. The frequency depends on the difference in energy between the orbitals. Explaining this phenomenon was crucial to the development of quantum mechanics. The atomic spectrum of each chemical element is unique and is largely responsible for the color of matter. Atomic spectra can also be analyzed to determine the composition of objects, such as stars, that are far away. See more at orbital, See also spectrum.
- Atomic structure
the structure of an atom, theoretically consisting of a positively charged nucleus surrounded and neutralized by negatively charged electrons revolving in orbits at varying distances from the nucleus, the constitution of the nucleus and the arrangement of the electrons differing with various chemical elements. Historical Examples We know comparatively little about atomic structure in relation […]
- Atomic theory
Physics, Chemistry. any of several theories describing the structure, behavior, and other properties of the atom and its component parts. Philosophy, (def 1). Historical Examples Out of the facts of chemistry the constructive imagination of Dalton formed the atomic theory. Fragments of science, V. 1-2 John Tyndall The atomic theory may be advantageously resorted to, […]
- Atomic time
noun time as measured by an atomic clock; International Atomic Time Examples Our clocks set with atomic time change themselves for daylight savings time. Word Origin 1937
- Atomic unit of length
. (in the Bohr atom) the radius of the electron orbit having the lowest energy.