1 Chapter 3 Electronic Structure and Periodic Law 3.4 Electronic Configurations Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Definitions Electronic configurations are detailed arrangement of electrons indicated by a specific notation, 1s 2,2s 2,2p 4,etc or drawing. Hund’s rule is a statement of the behavior of electrons when they occupy orbitals: Electrons will not join other electrons in an orbital of the same energy is available for occupancy. Pauli’s exclusion principle is a statement of the behavior of electrons when they occupy orbitals: Only electrons spinning in opposite directions can simultaneously occupy the same orbital.

3 Sample energy level diagram

4 The Atomic Orbital Model: Electronic Configurations

5 Valence Electrons or Shell The valence electrons or valence shells determine the chemical properties of the elements. are the electrons in the highest energy level. are related to the group number of the element. Example: Phosphorus has 5 valence electrons. 5 valence electrons P Group 5A(15) 2, 8, 5

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7 Run the following web animations/movies. 3.3: Atomic Subshell Energies

Table 3-2, p. 52

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Fig. 3-10a, p. 56

Fig. 3-10b, p. 56

An aid to remembering subshell filling order.

15 Noble Gas Configuration Nobel gas configuration is an electronic configuration in which the last eight electrons occupy and fill the s and p subshells of the highest occupied shell. (note in chapter 4, we will see that these noble gas configurations are important in understanding stability and bonding that occurs between atoms)