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Electron Configurations

Electron Configurations. Aufbau Principle “electrons are lazy”. the number of electrons in an atom is equal to the atomic number; each added electron will enter the orbitals in the order of increasing energy . Hund’s Rule “electrons don’t like each other”.

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Electron Configurations

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  1. Electron Configurations

  2. Aufbau Principle “electrons are lazy” • the number of electrons in an atom is equal to the atomic number; • each added electron will enter the orbitals in the order of increasing energy

  3. Hund’s Rule “electrons don’t like each other” • every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin.

  4. Orbital Notation • draw a box / line for each orbital. • Remember that s, p, d, and f subshells contain 1, 3, 5, and 7 degenerate (equal energy) orbitals, respectively. • Remember that an orbital can hold 0, 1, or 2 electrons only • If there are two electrons in the orbital, they must have opposite (paired) spins (Pauli principle )

  5. Orbital Notation • within a subshell (depicted as a group of boxes / lines), spread the electrons out (Hund's rule) • One electron in each degenerate orbital before they “double-up”

  6. Electron Configurations • a list showing how many electrons are in each orbital or subshell in an atom or ion • subshell notation: list subshells of increasing energy, with number of electrons in each subshell as a superscript • ground state configurations fill the lowest energy orbitals first

  7. Electron Configurations - examples • 1s2 2s2 2p5 means: • "2 electrons in the 1s subshell, 2 electrons in the 2s subshell, and 5 electrons in the 2p subshell" • 1s2 2s2 2p6 3s2 3p3 means: • 2 electrons have n=1 (in the 1s subshell); 8 electrons have n=2 (2 in the 2s subshell, and 6 in the 2p subshell); and 5 electrons have n=3 (2 in the 3s subshell, and 3 in the 3p subshell).

  8. Orbital Filling • http://www.colorado.edu/physics/2000/applets/a2.html • http://intro.chem.okstate.edu/WorkshopFolder/Electronconfnew.html

  9. Color Code Periodic Table

  10. Electron Configurations

  11. Orbital Notation

  12. Electron Configuration

  13. Electron Configurations Exceptions to Aufbau • A d subshell that is half-filled or full (ie 5 or 10 electrons) is more stable than the s subshell of the next shell. This is the case because it takes less energy to maintain an electron in a half-filled d subshell than a filled s subshell.

  14. Electron Configurations Exceptions to Aufbau • For instance, copper (atomic number 29) has a configuration of [Ar]4s1 3d10, not [Ar]4s2 3d9 as one would expect by the Aufbau principle. • Likewise, chromium (atomic number 24) has a configuration of [Ar]4s1 3d5, not [Ar]4s2 3d4.

  15. Work these on your own in your vodcast notes: • Write the orbital notation for Nickel • Write the electron configuration for Uranium

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