An atomic orbital is a mathematical description of the region in which an
electron may be found around a single
atom. Specifically, atomic orbitals are the possible
quantum states of the individual electrons in the
electron cloud around a single atom. Classically, the electrons were thought to orbit the atomic nucleus, much like the planets around the Sun (or more accurately, a moth orbiting very quickly around a lamp). Explaining the behavior of the electrons that "orbit" an atom was one of the driving forces behind the development of
quantum mechanics. In quantum mechanics, atomic orbitals are described as
wave functions over space, indexed by the n, l, and m
quantum numbers of the orbital or by the names as used in
electron configurations, as shown on the right. As electrons cannot be described as solid particles (as a planet or a moth) in this way, a more accurate analogy would be that of a huge atmosphere, the spatially distributed electron, around a tiny planet which is the atomic nucleus. Hence the term "orbit" was substituted with something else: orbital.
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