Transcript Chemistry - Manistique Area Schools

Chemistry
Chapter 9 Notes #3
Representing Molecules
• Molecular Formula
Structural/ Lewis Formula
– Ex. CH4
– Ex. H2O
Ball & Stick Model
Space Filling
Model
Exceptions to the Octet
• Expanded Octet
Odd # valence e-
– Ex. PCl5
– Due to a d e-
Less
than 8 eThe odd # and the
less than 8 tend to
bond with other
molecules
Molecular Shape
• VSEPR Model
– Valence shell electron pair repulsion model
– Used to determine the shape, or geometry, of
a molecule
– The angle formed by any 2 terminal atoms
and the central atom = bond angle
– Pairs of electrons repel each other
– Pairs are take up more space (they are only
attracted to one nuclei)
Molecular Shape
• Common Shapes
• 1. Linear
– No lone pairs of
electrons
– Atoms are at a 180
degree angle from
each other
Molecular Shape
• Common Shapes
• 2. Trigonal Planar
– No lone pairs on
the central atom
– 3 shared pairs
– Central atom has
3 terminal atoms
attached’
– Bond angle = 120
degrees
Molecular Shape
• Common Shapes
• 3. Tetrahedral
– No lone pairs
on the central
atom
– Central atom
has 4 terminal
atoms attached
– 4 shared pair
– Bond angle =
109.5 degrees
Molecular Shape
• Common Shapes
• 4. Bent
– 2 lone pairs
– 2 shared pair
– Central atom has 2 terminal atoms attached
– Bond angle = 105 degrees
Molecular Shape
• Common Shapes
• 5. Trigonal
Pyramidal
– 1 lone pairs
– Central atom
has 3 terminal
atoms
attached’
– Bond angle =
107 degrees
Review
Bent
Trigonal
Pyramidal