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Lecture 5

CHEM 11100 Lecture Notes - Lecture 5: Molecular Orbital Theory, Robert S. Mulliken, Electron Affinity


Department
Chemistry
Course Code
CHEM 11100
Professor
David Mazziotti
Lecture
5

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CHEM 11100 Lecture 5
Electronegativity
oCovalent bond between atoms A and B is stronger than averaging A-A and B-B
oElectronegativity increases as you go up and to the right on the periodic table
Bond polarity
oF2: X = 0, nonpolar (X < 0.5)
oHF: X = 4.0 – 2.1 = 1.9, polar covalent (X is between 0.5 and 2.0), dipole moment
oLiF: X = 4.0 – 1.0 = 3.0, ionic (X > 2.0)
Robert Mulliken
o1921: PhD from UChicago under Millikan
o1966: Nobel Prize for molecular orbital theory
o1934: energy definition; XA = 0.5(ionization energy + electron affinity) where XA is
the energy of atom A
oIonization energy: energy required to remove 1 mole of electrons from 1 mole of
gaseous atoms or molecules
Increases as you go up and to the right on the periodic table, including
noble gases
X  X+ + e
oElectron affinity: energy released when electron is attached to a neutral atom or
molecule
Increases as you go up and to the right on the periodic table
X + e  X
G.N. Lewis
oPhD from Harvard and professor at UC-Berkeley
o1902: Lewis dot structures
o1926: coined the word “photon”
Lewis dot structures
oClassical description of chemical bond
oAtoms obey the octet rule (8 electrons)
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