Electron Configuration Ch. 4 - Electrons in Atoms Electron Configuration

Maximum Number of Electrons In Each Sublevel Sublevel Number of Orbitals of Electrons s 1 2 p 3 6 d 5 10 f 7 14 LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 146

Electron capacities Electron capacities Copyright © 2006 Pearson Benjamin Cummings. All rights reserved.

Writing Electron Configurations Way to show the arrangement of electrons in an atom Parts: 1s2 1 = energy level s = sublevel 2 = number of electrons 1s2 2s2 2p4

Sublevels 4f 4d 4p 4s n = 4 3d 3p 3s n = 3 Energy 2p 2s n = 2 1s n = 1 1s22s22p63s23p64s23d104p65s24d10… Electron configuration of an element is the arrangement of its electrons in its atomic orbitals One can obtain and explain a great deal of the chemistry of the element by knowing its electron configuration 2p 2s n = 2 1s n = 1

S 16e- 1s2 2s2 2p6 3s2 3p4 S 16e- [Ne] 3s2 3p4 Notation Core Electrons Longhand Configuration S 16e- 1s2 2s2 2p6 3s2 3p4 Core Electrons Valence Electrons Shorthand Configuration S 16e- [Ne] 3s2 3p4

Filling Rules for Electron Orbitals Aufbau Principle: Electrons are added one at a time to the lowest energy orbitals available until all the electrons of the atom have been accounted for. Pauli Exclusion Principle: An orbital can hold a maximum of two electrons. To occupy the same orbital, two electrons must spin in opposite directions. Hund’s Rule: Electrons occupy equal-energy orbitals so that a maximum number of unpaired electrons results. *Aufbau is German for “building up”

General Rules Aufbau Principle Electrons fill the lowest energy orbitals first. “Lazy Tenant Rule”

Order in which subshells are filled with electrons 2p 3p 4p 5p 6p 3d 4d 5d 6d 4f 5f 2 2 6 2 6 2 10 6 2 10 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d …

Examples Chlorine Bromine Calcium

General Rules Pauli Exclusion Principle Each orbital can hold TWO electrons with opposite spins.

Notation Orbital Diagram 1s 2s 2p O 8e-

General Rules WRONG RIGHT Hund’s Rule Within a sublevel, place one e- per orbital before pairing them. “Empty Bus Seat Rule” WRONG RIGHT

H = 1s1 He = 1s2 Li = 1s2 2s1 Be = 1s2 2s2 C = 1s2 2s2 2p2 S THIS SLIDE IS ANIMATED IN FILLING ORDER 2.PPT H = 1s1 1s He = 1s2 1s Li = 1s2 2s1 1s 2s Be = 1s2 2s2 1s 2s C = 1s2 2s2 2p2 1s 2s 2px 2py 2pz S = 1s2 2s2 2p43s23p4 1s 2s 2px 2py 2pz 3s 3px 3py 3pz

Fe = 1s1 2s22p63s23p64s23d6 26 Iron has ___ electrons. Arbitrary 2px 2py 2pz 3s 3px 3py 3pz 4s 3d 3d 3d 3d 3d Arbitrary Energy Scale 18 32 8 2 1s 2s 2p 3s 3p 4s 4p 3d 5s 5p 4d 6s 6p 5d 4f NUCLEUS e- e- e- e- e- e- e- e- e- e- e- e- e- +26 e- e- e- e- e- e- e- e- e- e- e- e- e-

Examples Nitrogen Aluminum

Shorthand Configuration Element symbol Electron configuration Ca [Ar] 4s2 V [Ar] 4s2 3d3 F [He] 2s2 2p5 Ag [Kr] 5s2 4d9 I [Kr] 5s2 4d10 5p5 Xe [Kr] 5s2 4d10 5p6 Fe [He] 2s22p63s23p64s23d6 [Ar] 4s23d6 Sg [Rn] 7s2 5f14 6d4