9 05 sep 13 1 the statement that the lowest energy

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Unformatted text preview: -13 1. The statement that “the lowest energy configuration for an atom is the one having the maximum number of unpaired electrons allowed by the Pauli principle in a particular set of degenerate orbitals” is known as: a. The Aufbau principle b. Hund’s Rule c. Heisenberg Uncertainty Principle d. The Pauli Exclusion Principle. 2. a. b. c. d. Which of the following electron configurations is not possible? 1s2 2s2 2p3 1s2 2s2 2p6 1s2 2s2 2p6 2d2 1s2 2s2 2p6 3s1 Example. What are the electron configurations for the following elements? Ca V Ni Electron configurations and noble gases Writing out electron configurations can be long and tedious. However, there are shortcuts. Consider the following: Ne 1s2 2s2 2p6 Mg 1s2 2s2 2p6 3s2 [Ne] ___________ Ar 1s2 2s2 2p6 3s2 3p6 K 1s2 2s2 2p6 3s2 3p6 4s1 [Ar] 4s1 10 05-Sep-13 Exceptions to the Aufbau principle For Cr we expect the electron configuration to be [Ar]4s23d4. Experimentally we see [Ar]4s13d5. Why? 3d ____ 4s ____ 3p ____ 3s ____ 2p ____ 2s ____ 1s ____ ____ ____ ____ ____ ____ ____ ____ The reason for this exception is not completely understood, but it seems that a half-filled 3d subshell (for Cr) lends a special stability to the observed electron configuration. ____ Similar exceptions are foun...
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This document was uploaded on 02/18/2014.

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