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  2. Aufbau principle - Wikipedia

    en.wikipedia.org/wiki/Aufbau_principle

    Electron behavior is elaborated by other principles of atomic physics, such as Hund's rule and the Pauli exclusion principle. Hund's rule asserts that if multiple orbitals of the same energy are available, electrons will occupy different orbitals singly and with the same spin before any are occupied doubly. If double occupation does occur, the ...

  3. Hund's rules - Wikipedia

    en.wikipedia.org/wiki/Hund's_rules

    However Hund's rules should not be used to order states other than the lowest for a given configuration. [5] For example, the titanium atom ground state configuration is ...3d 2 for which a naïve application of Hund's rules would suggest the ordering 3 F < 3 P < 1 G < 1 D < 1 S. In reality, however, 1 D lies below 1 G.

  4. Pauli exclusion principle - Wikipedia

    en.wikipedia.org/wiki/Pauli_exclusion_principle

    In quantum mechanics, the Pauli exclusion principle (German: Pauli-Ausschlussprinzip) states that two or more identical particles with half-integer spins (i.e. fermions) cannot simultaneously occupy the same quantum state within a system that obeys the laws of quantum mechanics.

  5. Electron configurations of the elements (data page) - Wikipedia

    en.wikipedia.org/wiki/Electron_configurations_of...

    As an approximate rule, electron configurations are given by the Aufbau principle and the Madelung rule. However there are numerous exceptions; for example the lightest exception is chromium, which would be predicted to have the configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 4 4s 2 , written as [Ar] 3d 4 4s 2 , but whose actual configuration given ...

  6. Molecular orbital diagram - Wikipedia

    en.wikipedia.org/wiki/Molecular_orbital_diagram

    The next step in constructing an MO diagram is filling the newly formed molecular orbitals with electrons. Three general rules apply: The Aufbau principle states that orbitals are filled starting with the lowest energy; The Pauli exclusion principle states that the maximum number of electrons occupying an orbital is two, with opposite spins

  7. Hund's rule of maximum multiplicity - Wikipedia

    en.wikipedia.org/wiki/Hund's_Rule_of_Maximum...

    Hund's rule of maximum multiplicity is a rule based on observation of atomic spectra, which is used to predict the ground state of an atom or molecule with one or more open electronic shells. The rule states that for a given electron configuration , the lowest energy term is the one with the greatest value of spin multiplicity . [ 1 ]

  8. Electron configuration - Wikipedia

    en.wikipedia.org/wiki/Electron_configuration

    The aufbau principle (from the German Aufbau, "building up, construction") was an important part of Bohr's original concept of electron configuration. It may be stated as: [ 13 ] a maximum of two electrons are put into orbitals in the order of increasing orbital energy: the lowest-energy subshells are filled before electrons are placed in ...

  9. Quantum number - Wikipedia

    en.wikipedia.org/wiki/Quantum_number

    The occupation of the electron states in such an atom can be predicted by the Aufbau principle and Hund's empirical rules for the quantum numbers. The Aufbau principle fills orbitals based on their principal and azimuthal quantum numbers (lowest n + l first, with lowest n breaking ties; Hund's rule favors unpaired electrons in the outermost ...