Ch 221 Exam #2 Study Outline
Winter, 2014
NOTE: Use this outline at your own risk. Hopefully I haven't forgotten anything, but sometimes I
do! It is meant to be a study aid and is not meant to be a replacement for actually reviewing the
lecture notes and homework assignments.
Ch 4 – Chemical Bonding - Understanding Climate Change
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Difference between ionic, covalent, and metallic bonds
Energy of an ionic bond depends on the charge and the distance
Lewis symbols
Lewis structure for ionic compounds
Lewis structures for molecular (covalent) compounds
single, double and triple bonds
2Lewis structures for charged species like CO3 ,etc
trends in electronegativity
polar covalent compounds
predicting polar covalent vs. ionic bonds
resonance hybrids or structures
formal charge and Lewis structures
Exceptions to the Octet Rule: (1) less than 8 valence electrons for Group 3A, (2) expanded octets
rd
when the central atom is in the 3 period or higher, (3) odd-electron species (free radicals)
Ch 5 - Bonding Theories: Explaining Molecular Geometry
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VSEPR Theory
Steric
Number
2
Electron Group
Geometry
Linear
3
Trigonal planar
4
Tetrahedral
Trigonal Bipyramidal
5
5
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NOTE: lone pairs are
equatorial
Octahedral
Bond Angles
Molecular Geometry
o
180
o
120
o
109.5
o
equatorial = 120 ,
o
axial = 90 to the
equatorial plane
o
90
Linear
Trigonal Planar
Bent
Tetrahedral
Trigonal Pyramidal
Bent
Trigonal Bipyramidal
Seesaw
T-shaped
Linear
Octahedral
Square Pyramidal
Square Planar
Number of
Lone Pairs
0
0
1
0
1
2
0
1
2
3
0
1
2
Applying VSEPR theory - (1) Lewis structure, (2) count electron groups around central atom, (3)
determine appropriate VSEPR electron group geometry first, (4) then determine molecular
geometry based on the number of lone pairs and the position of atoms in space
Remember: Multiple bonds count as one electron group in VSEPR theory
Polar bonds and polar molecules - predicting molecular polarity, show the net dipole moment
The effect of LP-LP, LP-BP, and BP-BP repulsions
More →
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Valence Bond Theory – hybrid orbitals
Steric
Number
2
3
4
5
6
Electron Group Geometry
Linear
Trigonal planar
Tetrahedral
Trigonal Bipyramidal
Octahedral
Hybrid Orbitals
and number of
each (same as
steric number)
sp (2)
2
sp (3)
3
sp (4)
3
sp d (5)
3 2
sp d (6)
Number of Unhybridized
p-orbitals and therefore
number of -bonds
2
1
0
0
0
Procedure:
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Hybridize the CENTRAL ATOM ONLY (others as needed – will be told if necessary)
Only use valence shell electrons
The number of hybrid orbitals formed = number of atomic orbitals used
Hybrid orbitals get 1 electron for a -bond, 2 electrons for a lone pair.
Be able to illustrate hybridization for simple molecules using orbital diagrams, showing ,  bonds, and
lone pairs. For example:
More →
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Molecular Orbital Theory
o
o
o
o
bonding and antibonding orbitals
given MO energy diagrams, be able to fill in the MO’s
calculate bond order and be able to predict if molecule exists
predict magnetism (paramagnetic or diamagnetic).
Examples: