Lewis Structures
and Molecular Shape
Lewis Dot Diagrams
Lewis Structures and Quantum Mechanics
Valence bond
Theory (Pauling):
covalent bonds
share e- by
overlapping orbitals
Draw an orbital
diagram to show
the bonding in
H2O
p. 227 #4
p. 230 #3
Lewis Structures
• Use the summaries on p. 225 and p. 229 to
complete:
p. 227 #5, p. 229 #10, 11, p. 230 #4,5
p. 229 #12 (extension)
Draw Lewis diagrams of:
Sb
Sr2+
BrCS2
NH4+
HPO32PCl5
Molecular Shapes and Optical Activity
• Unpolarized light (normal
light) runs in all directions
• Polarization is confining the
vibration of a wave to one
direction
• Polarizer: a filter that only
allows light waves in a
particular direction to pass
• Various shapes will absorb
and deflect the polarized light
in different ways
Molecular Shapes
Why do molecules take
on these shapes?
Molecular Shape
VSEPR Theory
• valence shell e- pairs repel each other
electrostatically so as to minimize repulsive forces
• lone pairs are bulkier (occupy more space) and repel
bonded pairs of e- more strongly
Task:
Build models of molecules in tables from p. 243-245
in text. Draw 3-D diagrams, write shape name and
label bond angles for each molecule.
Homework
•
•
•
•
p. 246 #1-4
p. 249 #10,11
p. 250 #1-3
p. 247 #9 (extension)