Filling Rules for Electron Orbitals Aufbau Principle Electrons

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 6 s 6 p 5 d 4 f have been accounted for. 32 5 s 5 p 4 d Pauli Exclusion Principle: An orbital can hold a maximum of two electrons. 4 s 4 p 3 d 18 To occupy the same orbital, two electrons must spin in opposite 18 directions. Arbitrary North South 3 s Energy Scale - 3 p - 8 2 s 2 p Hund’s Rule: Electrons occupy equal-energy orbitals so that a maximum number of unpaired electrons results. 8 1 s *Aufbau is German for “building up” S N NUCLEUS 2

Spin Quantum Number, ms North South - - S N The electron behaves as if it were spinning about an axis through its center. This electron spin generates a magnetic field, the direction of which depends on the direction of the spin. Brown, Le. May, Bursten, Chemistry The Central Science, 2000, page 208

Energy Level Diagram of a Many-Electron Atom 6 s 6 p 5 d 4 f 32 5 s 5 p 4 d 18 4 s 4 p 3 d 18 Arbitrary Energy Scale 3 s 3 p 8 2 s 2 p 8 1 s 2 NUCLEUS O’Connor, Davis, Mac. Nab, Mc. Clellan, CHEMISTRY Experiments and Principles 1982, page 177

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

Quantum Numbers n shell 1, 2, 3, 4, . . . l subshell 0, 1, 2, . . . n - 1 ml orbital - l. . . 0. . . +1 ms electron spin +1/2 and -1/2

Electron Configuration Filling-Order of Electrons in an Atom

Order in which subshells are filled with electrons 1 s 2 s 2 p 3 s 3 p 3 d 4 s 4 p 4 d 4 f 5 s 5 p 5 d 5 f 6 s 6 p 6 d 7 s 2 2 6 2 10 1 s 2 s 2 p 3 s 3 p 4 s 3 d 4 p 5 s 4 d …

Sublevels 4 f 4 d Energy 6 d 5 f 7 s 6 p 5 d 4 f 6 s 5 p 4 d 5 s 4 p 3 d 4 s 3 p 6 d 7 s 6 s 5 p 5 s 4 p 4 s 5 d 4 f n=3 3 d 2 p 3 s 2 p 2 s 4 p 3 d 4 s 3 p 3 s 4 d 3 p 3 s 2 p 2 s 6 p 5 f Energy n=4 n=2 2 s 1 s 1 s n=1 1 s

4 f Sublevels 4 d s p s d p s n=4 f d p Energy s n=3 4 p 3 d 4 s 3 p 3 s 1 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 10… 2 p n=2 2 s n=1 1 s

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”

Energy Level Diagram of a Many-Electron Atom 6 s 6 p 5 d 4 f 32 5 s 5 p 4 d 18 4 s 4 p 3 d 18 Arbitrary Energy Scale 3 s 3 p 8 2 s 2 p 8 1 s 2 NUCLEUS O’Connor, Davis, Mac. Nab, Mc. Clellan, CHEMISTRY Experiments and Principles 1982, page 177

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Hydrogen 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La H = 1 s 1

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Helium 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La He = 1 s 2

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Lithium 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La Li = 1 s 22 s 1

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Carbon 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La C = 1 s 22 p 2

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Nitrogen 4 f Bohr Model N 2 s 2 p Hund’s Rule “maximum number of unpaired orbitals”. 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La N = 1 s 22 p 3

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Fluorine 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La F = 1 s 22 p 5

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Aluminum 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La Al = 1 s 22 p 63 s 23 p 1

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Argon 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La Ar = 1 s 22 p 63 s 23 p 6

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Iron 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe = 1 s 22 p 63 s 23 p 64 s 23 d 6 Fe La

Arbitrary Energy Scale Energy Level Diagram 6 s 6 p 5 d 5 s 5 p 4 d 4 s 4 p 3 d 3 s 3 p Lanthanum 4 f Bohr Model N 2 s 2 p 1 s Electron Configuration NUCLEUS H He Li C N Al Ar F CLICK ON ELEMENT TO FILL IN CHARTS Fe La La = 1 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 66 s 25 d 1

Shorthand Configuration A neon's electron configuration (1 s 22 p 6) B third energy level [Ne] 3 s 1 C D one electron in the s orbital shape Na = [1 s 22 p 6] 3 s 1 electron configuration

Shorthand Configuration Element symbol Electron configuration Ca [Ar] 4 s 2 V [Ar] 4 s 2 3 d 3 F [He] 2 s 2 2 p 5 Ag [Kr] 5 s 2 4 d 9 I [Kr] 5 s 2 4 d 10 5 p 5 Xe [Kr] 5 s 2 4 d 10 5 p 6 Fe Sg 22 p 64 s [He] 2 s[Ar] 3 s 223 d 3 p 564 s 23 d 5 [Rn] 7 s 2 4 f 14 5 d 4

General Rules • Pauli Exclusion Principle – Each orbital can hold TWO electrons with opposite spins. Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

General Rules 6 d Aufbau Principle 7 s 6 p 5 d – Electrons fill the lowest energy orbitals first. 6 s 4 d 3 p 7 s 5 f 6 p 5 d 6 s 5 p 5 s 4 p 4 s 6 d 4 f 5 p Energy – “Lazy Tenant Rule” 5 f 4 d 5 s 3 d 4 p 3 d 4 s 3 p 3 s 3 s 2 p 2 p 2 s 2 s 1 s 1 s Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem 4 f

General Rules • Hund’s Rule – Within a sublevel, place one electron per orbital before pairing them. – “Empty Bus Seat Rule” WRONG RIGHT Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem

O Notation 15. 9994 • Orbital Diagram O 8 e- 1 s 2 s • Electron Configuration 2 2 4 1 s 2 s 2 p Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem 8 2 p

Notation S 32. 066 • Longhand Configuration S 16 e 6 2 2 2 1 s 2 s 2 p 3 s Core Electrons S 16 e 4 3 p Valence Electrons • Shorthand Configuration 2 4 [Ne] 3 s 3 p Courtesy Christy Johannesson www. nisd. net/communicationsarts/pages/chem 16