ELECTRON CONFIGURATION

Updated 05-May-2020.

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Configuration irregularities: deviations from the Madelung rule and inversion of orbital energy levels: (a) The electron configurations of many atoms that do not obey the Madelung rule of orbital occupancy can be explained by minimum-energy configurations obtained from the Dirac Hyper Hartree-Fock equations. The resulting non-integral occupation of ns and ( n-1)d orbitals (the usual interpretation for energy band calculations in solids) explains eight of the ten `anomalous’ configurations. (b) All four d- and f-block atoms whose singly charged cations result from the loss of an ( n-1)d electron rather than an ns electron are shown to have ( n-1)d rather than ns as their highest occupied energy levels.

My botty best at summarizing from Wikipedia: electron configuration is the distribution of electrons in atomic or molecular orbitals . electrons move independently in an orbital, in an average field created by all other orbitals. configurations are described by Slater determin knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elements . in bulk materials, this same idea helps explain the peculiar properties of lasers and semiconductors . a subshell is the set of states defined by a common azimuthal quantum number, l . the values l = 0, 1, 2, 3 correspond to the s, p, d, and f labels the maximum number of electrons that can be placed in a subshell is given by 2(2l+1) this gives two electrons in an s subshell, six electrons at a p subshell and ten hydrogen has one electron in the s-orbital of the first shell, so its configuration is written 1s1 . for atoms with many electrons, this notation can become lengthy and so an abbreviated the portion of its configuration that is equivalent to neon is abbreviated as [Ne] 3s2 3p3 . this convention is useful as it is the electrons in the outermost shell that most determine the chemistry the letters of the orbital labels (s, p, d, f) are written in an italic or slanting typeface . the International Union of Pure and Applied Chemistry recommends a normal “sharp”, “principal”, “diffuse” and “fundamental” (or “fine”) orbitals with azimuthal quantum number, l, of 0, 1, 2 or 3 respectively . mole sodium atoms can move from one configuration to another by absorbing or emitting energy . in a sodium-vapor lamp for example, sodium-atoms are excited to the 3p level by an electrical discharge . sodium the excitation of core electrons is possible, but requires much higher energies, generally corresponding to x-ray photons . the remainder of this article deals only with the ground-state configuration, often referred to as chemists believed in atoms long before the physicists . Langmuir began his paper referenced above by saying . valence electrons in the atom were described by Richard Abegg in 1904 . in 1924, E. C. Stoner correctly predicted the shell structure of sulfur to be 2.8.6 . neither Boh the Schrödinger equation gives three of the four quantum numbers . this solution yields the atomic orbitals that are shown today in textbooks of chemistry . the modern form of the aufbau principle describes an order of orbit where two orbitals have the same value of n+l, they are filled in order of increasing n . the aufbau principle can be applied to the protons and neutrons in the atomic nucleus . madelung’s rule considers atomic orbitals as “boxes” of fixed energy into which can be placed two electrons . energy of an electron “in” an orbital depends on the energies of all the other the aufbau principle is based on an approximation . there is an almost-fixed filling order at all . in a hydrogen-like atom, the s-orbital and the p- after calcium, most neutral atoms in first series of transition metals have configurations with two 4s electrons . there are exceptions: Chromium and copper have electron configurations [Ar] 3d5 4s the first electrons to be ionized come from the 4s-orbital . this interchange of electrons between 4s and 3d is found for all atoms . energy order of atomic orbitals is there is no special reason why the Fe2+ ion should have the same electron configuration as the chromium atom . the chemistry of the two species is very different . the electron configuration of the central chromium atom is described as 3d6 . six electrons fill the three lower-energy d orbitals between the ligands . the other two d-like orbit special relativity effects tend to decrease the energy of the s-orbitals . the table below shows the ground state configuration in terms of orbital occupancy . in the transition metals, the 4s orbital is of the electron-shell configuration of elements beyond hassium has not yet been empirically verified . but they are expected to follow Madelung’s rule without exceptions until element 120 . beyond element 120, Madelung is expected to stop the paramagnetism of dioxygen was a major success for molecular orbital theory . the electronic configuration of polyatomic molecules can change without absorption or emission of a photon . electron configurations have computational chemistry typically attempts to make quantitative estimates of chemical properties . not all methods in calculational chemistry rely on electron configuration: density functional theory . for atoms or molecules with more than one electron, motion of electrons a fundamental application of electron configurations is in the interpretation of atomic spectra . term symbols describe the different energy levels available to an atom . Term symbols can be calculated for any electron configuration, not just ground- ground-state electron configurations of the elements were experimentally determined . analysis of atomic spectra reveals ground state electron configuration of elements .