Electron Configurations

Opening Questions

Electron Shells and Subshells We arranged electrons into “shells” labeled n = 1, 2, 3 to indicate the 1st shell, the 2nd shell, etc. Each “shell” has further divisions called subshells – designated s, p, d, and f.

Electron Configurations Basic idea: electrons occupy lowest energy levels available n = 1 n = 2 2e Carbon’s subshells Where do subshells start? s: 1st energy level p: 2nd energy level d: 3rd energy level f: 4th energy level

Electron Configuration Notation Electron configuration: a list of all the subshells that have electrons for a given element Notation: 1 number of electrons in subshell 1 s subshell value of energy level

Electron Configurations Which element has the configuration 1s22s22p5? Period 1 2 3 4 5 6 7 1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 2p 3p 4p 5p 6p 4f 5f Periodic Table: Subshells 2 elements 10 elements 6 elements 14 elements

Electron Configurations Write the electron configuration for this element. Period 1 2 3 4 5 6 7 1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 2p 3p 4p 5p 6p 4f 5f Periodic Table: Subshells 2 elements 10 elements 6 elements 14 elements How many e- in each subshell? s: 2 electrons p: 6 electrons d: 10 electrons f: 14 electrons

Wrap-up Identify the element with the following electron configuration. 1s22s22p63s22p64s23d104p3 What is the outermost subshell for bromine, Br? Name an element with electrons in the f-block. What is the electron configuration for the element with the atomic number 13? How many valence electrons does krypton, Kr, have? How do you know?

Shorthand Electron Configurations Instead of writing out all the filled subshells, you can use a shorthand (or noble gas) configuration. Use the last noble gas as your starting point. EXAMPLE: Bromine’s full electron configuration: 1s22s22p63s23p64s23d104p5 Bromine’s shorthand configuration: [Ar]4s23d104p5

Shorthand Electron Configurations Write the shorthand electron configuration for this element Period 1 2 3 4 5 6 7 1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 2p 3p 4p 5p 6p 4f 5f Periodic Table: Subshells 2 elements 10 elements 6 elements 14 elements

PRACTICE! Go Figure Worksheet… Start on the backside: - question #3 b) and d)

D-block Elements Period 1 2 3 4 5 6 7 1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 2p 3p 4p 5p 6p 4f 5f Periodic Table: Subshells 2 elements 10 elements 6 elements 14 elements The d-block elements do not follow the nice pattern seen in groups 1, 2, 13-18. D-block elements tend to have 2 valence electrons because the s-block before them is full. Those s-block electrons are the valence electrons. However, it is possible for the first 5 d-block electrons to be valence electrons.