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Electron configuration
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<p>In <a href="/facts/Atomic_physics/7Jlm4I7k">atomic physics</a> and <a href="/facts/Quantum_chemistry/H9AXV0lx">quantum chemistry</a>, the electron configuration is the <a href="/facts/Distribution_(mathematics)/yfaJ4mUp">distribution</a> of <a href="/facts/Electron/L0KBo5cW">electrons</a> of an <a href="/facts/Atom/69syB8dH">atom</a> or <a href="/facts/Molecule/N9ljSfFq">molecule</a> (or other physical structure) in <a href="/facts/Atomic_orbital/tKhgl6mL">atomic</a> or <a href="/facts/Molecular_orbital/0dP30jaa">molecular orbitals</a>. For example, the electron configuration of the <a href="/facts/Neon/5bF1FwGL">neon</a> atom is 1s2 2s2 2p6, meaning that the 1s, 2s, and 2p <a href="/facts/Electron_shell/QxI30eh9">subshells</a> are occupied by two, two, and six electrons, respectively. </p><p>Electronic configurations describe each electron as moving independently in an <a href="/facts/Atomic_orbital/tKhgl6mL">orbital</a>, in an average <a href="/facts/Field_(physics)/FJdAKeRA">field</a> created by the <a href="/facts/Atomic_nucleus/orpIm5Xl">nuclei</a> and all the other electrons. Mathematically, configurations are described by <a href="/facts/Slater_determinants/oKfv2Av0">Slater determinants</a> or <a href="/facts/Configuration_state_function/ouDKnRms">configuration state functions</a>. </p><p>According to the laws of <a href="/facts/Introduction_to_quantum_mechanics/p57bzH1Y">quantum mechanics</a>, a <a href="/facts/Energy_level/66x51Khc">level of energy</a> is associated with each electron configuration. In certain conditions, electrons are able to move from one configuration to another by the emission or absorption of a <a href="/facts/Quantum/4x5QTxGB">quantum</a> of energy, in the form of a <a href="/facts/Photon/mFNhAEzA">photon</a>. </p><p>Knowledge of the electron configuration of different atoms is useful in understanding the structure of the <a href="/facts/Periodic_table/umdGIfUb">periodic table of elements</a>, for describing the <a href="/facts/Chemical_bond/ArNUMnIB">chemical bonds</a> that hold atoms together, and in understanding the <a href="/facts/Chemical_formula/hghUtthl">chemical formulas</a> of compounds and the <a href="/facts/Molecular_geometry/7USG5zDn">geometries of molecules</a>. In bulk materials, this same idea helps explain the peculiar properties of <a href="/facts/Lasers/jk6PTvvT">lasers</a> and <a href="/facts/Semiconductors/zFf3mGTE">semiconductors</a>. </p>