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Outer Electron Configurations.notebook October 25, 2009 Classifying elements by group, period, and block Outer electron configurations Involves the electrons in the highest occupied energy level Can also include electrons in the d and f sublevels under the following conditions: The sublevel is incomplete OR The element is in the same period as the completed sublevel. Oct 2910:08 PM Examples of outer electron configurations: 1 1 Na [Ne] 3s Outer electron config. 3s 2 5 2 5 Cl [Ne] 3s 3p Outer electron config. 3s 3p 2 7 2 7 Ni [Ar] 4s 3d Outer electron config. 4s 3d 2 7 1 2 7 1 Gd [Xe] 6s 4f 5d Outer electron config. 6s 4f 5d 2 14 10 4 2 14 10 4 Po [Xe] 6s 4f 5d 6p Outer electron config. 6s 4f 5d 6p Most easily identified as the entries at the end of the noble gas configuration. Oct 2910:18 PM 1 Outer Electron Configurations.notebook October 25, 2009 What's so important about electrons in that part of the configuration? Electrons in the outer configuration are the furthest away from the nucleus Most likely to be involved in chemical bonding Valence electrons From the outermost s and p sublevel The first electrons used in bonding Oct 2910:29 PM Patterns in the periodic table for outer electron configuration Group 1 Element Outer Electron Configuration 1 H 1s 1 Li 2s 1 Na 3s 1 K 4s 1 Rb 5s 1 Cs 6s 1 Fr 7s Oct 2910:33 PM 2 Outer Electron Configurations.notebook October 25, 2009 All group 1 elements have the same outer electron configuration pattern. 1 s n n = period number 2 Likewise, all group 2 elements follow the pattern s . n Oct 2910:41 PM For the main group elements Group Number Name Group Configuration 1 1 Alkali Metals ns 2 2 Alkaline Earth Metals s n 2 1 13 Boron Family s p n n 2 2 14 Carbon Family s p n n 2 3 15 Nitrogen Family ns np 2 4 16 Oxygen Family ns np 2 5 17 Halogens s p n n 2 6 18 Noble Gases s p n n Oct 2910:47 PM 3 Outer Electron Configurations.notebook October 25, 2009 Example 2 10 2 Given electron configuration [Kr] 5s 4d 5p identify the following about the element: Period Block Group Answer: Period corresponds to high occupied energy level 5 Block: Sublevel on final entry p 2 2 Group: Outer configuration matches ns np 14 Oct 309:11 PM Example Write the expected outer electron configuration for the element located at the following position on the periodic table: Group 16, Period 4 Answer: 2 4 4s 4p Notes: 2 4 The pattern ns np matches group 16 The 4 out front matches the period number Oct 309:17 PM 4
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