# Empty 1s li 2 cation full 1s orbital ½ full 2s

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Empty 1s Li 2+ Cation Full 1s orbital & ½ full 2s orbital Neutral Lithium Atom 3p + e - e - e - Z eff < 3+ e - ... 2s electron “ feels” less nuclear charge ... 2s electron “feels” full 3+ nucleus ... Less attractive force, easily removed ... Greater attractive force, difficult to remove ... 1s e -’ s shield the 2s e - from nucleus ... nothing shields 2s e - from nucleus ... 2s electron higher energy ... 2s electron lower energy

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Factors Affecting Electron Energies: 2s versus 2p (Low P.E.) 1s 2s 2p (High P.E.) Why should 2p be higher in energy than 2s? Question: Is it easier to remove a 2s electron or a 2p electron? radius nucleus Total Probability Answer: It is easier to remove the 2p electron. Node 2s Probability 2p Probability Significant probability that electron is near the nucleus. 2 s electron gets closer to nucleus stronger attraction! E s < E p < E d < E f
Quantum Mechanics: What are the electron energies? Bohr Model n=2 n=3 n=4 (High P.E.) n=1 (Low P.E.) 1s 2s 3s 4s Quantum Mechanical 2p 3p 3d 4p 4d 5s m l = -1, 0, +1 m l = -1, 0, +1 m l = -2, -1, 0, +1, +2 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p High P.E.

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Putting Electrons in Atoms: The Aufbau Principle Fill atomic orbitals with electrons beginning with the lowest P.E. orbital and working towards high P.E orbitals. Neutral Lithium Atom Li 6.941 3 3 p + 3 e - 1s 2s 2p 3s 3p m s = -½ m s = +½ Electron Configuration: 1s 2 2s 1
Putting Electrons in Atoms: The Aufbau Principle Neutral Carbon Atom C 12.01 6 6 p + 6 e - 1s 2s 2p 3s 3p m s = -½ m s = +½ Electron Configuration: 1s 2 2s 2 Hund’s Rule: Don’t pair electrons in an orbital until you have no choice. 2p 2 ...electron spins in same direction!

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Putting Electrons in Atoms: The Aufbau Principle Chlorine anion: Cl - Cl 35.45 17 17 p + 17+1 = 18 e - 1s 2s 2p 3s 3p Electron Configuration: 1s 2 2s 2 2p 6 3s 2 3p 6
Putting Electrons in Atoms: The Aufbau Principle Neutral Nickel Atom Ni 58.69 28 28 p + 28 e - 1s 2s 2p 3s 3p Electron Configuration: 1s 2 2s 2 2p 6 4s 3d 3s 2 3p 6 4s 2 3d 8 [Ar] 4s 2 3d 8 Argon’s electron configuration

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Electron Configuration: A closer look. [Ar] 3d 8 4s 2 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 8 Outer Electrons ...furthest from nucleus ...largest “n” value Valence Electrons ...a.k.a. bonding electrons Inner Core Electrons ...associated with noble gas Definitions: pg. 303
Electron Configurations: The Periodic Table 1s 1 1s 2 2s 1 2s 2 2p 1 2p 2 2p 3 2p 4 2p 5 2p 6 3s 1 3s 2 3p 1 3p 2 3p 3 3p 4 3p 5 3p 6 3d 1 3d 2 3d 3 3d 4 3d 5 3d 6 4s 1 4s 2 3d 7 3d 8 3d 9 3d 10 4p 1 4p 2 4p 3 4p 4 4p 5 4p 6 4d 1 4d 2 4d 3 4d 4 4d 5 4d 6 4d 7 4d 8 4d 9 4d 10 5d 1 5d 2 5d 3 5d 4 5d 5 5d 6 5d 7 5d 8 5d 9 5d 10 5p 1 5p 2 5p 3 5p 4 5p 5 5p 6 6p 1 6p 2 6p 3 6p 4 6p 5 6p 6 6d 1 6d 2 6d 3 6d 4 6d 5 6d 6 6d 7 5s 1 5s 2 6s 1 6s 2 7s 1 7s 2 “s” block “d” block “p” block

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Electron Configurations: The Periodic Table 1s 1 1s 2 2s 1 2s 2 2p 1 2p 2 2p 3 2p 4 2p 5 2p 6 3s 1 3s 2 3p 1 3p 2 3p 3 3p 4 3p 5 3p 6 3d 1 3d 2 3d 3 3d 4 3d 5 3d 6 4s 1 4s 2 3d 7 3d 8 3d 9 3d 10 4p 1 4p 2 4p 3 4p 4 4p 5 4p 6 4d 1 4d 2 4d 3 4d 4 4d 5 4d 6 4d 7 4d 8 4d 9 4d 10 5d 1 5d 2 5d 3 5d 4 5d 5 5d 6 5d 7

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