Chapter 10 Bonding Theory and Molecular Structure. Molecular Shapes The VSEPR model electron-pair geometries molecular geometries Molecular polarity Valence Bond Theory Covalent bonding and orbital overlap Hybrid orbitals sp hybrid orbitals sp 2 hybrid orbitals sp 3 hybrid orbitals
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Valence Shell Electron Pair Repulsion Theory: regions of electron density
(single, double, or triple bonds or lone pairs) arrange themselves around an
atom to be as far apart as possible (electron pair repulsion).
Electron pair geometries:
Electron pair geometry: tetrahedral
Molecular polarity physical and chemical properties
bonds:if DX > 0 polar bondA—B
molecules and ions: if dipoles do not exactly cancel, molecule will be polar
Bonds are formed using valence electrons and orbitals:
atomic orbitalsmolecular orbitals (covalent bonds)
But what about CH4?
Tetrahedral, all bonds
equivalent. How do we
get this from s and p a.o.s?
2 equivalent bonds
3 equivalent bonds
4 equivalent bonds
e– pair geometryhybridization
What is the hybridization of the central atom in each of the following?
trigonal planar = sp2
all six atoms lie
in same plane
linear = sp
What is the hybridization of each indicated atom in the following
molecule? How many sigma and pi bonds are in the molecule?
Fact: O2 is paramagnetic!
Valence bond theory
Overlap of wave functions:
Overlap of 1s orbitals:
(higher energy than
(lower energy than
(no. of e– in bonding m.o.s) - (no. of e– in antibonding m.o.s)
bond order =
b.o. = 1 (i.e., lower energy than separate atoms)
b.o. = 0
b.o. = 0.5
Overlap of 2s and 2p orbitals
2s s2s and s*2s
(same as 1s),
then 2p orbitals give:
(i.e., 8 a.o.s 8 m.o.s)
6 e– in a cyclic,
planar p system