1. Real Molecule Shapes
Any molecule containing only 2 atoms has a linear shape.
To predict shapes of molecules with more than 2 atoms we use VESPR theory
VESPR stands for VALENCE SHELL ELECTRON PAIR REPLUSION
Since electrons repel each other, electron pairs will be as far apart as possible.
Episode 503

2. 2 3 4 2 2 3 1 shape Bent Trigonal pyramidal Example Linear ( ⁰ angle)
Number of atoms bonded to central atom
Number of unshared pairs of electrons
Example
Linear
( ⁰ angle)
Trigonal planar
Tetrahedral
( ⁰ angle)
Bent
Trigonal pyramidal 2
180 3
120 4
109.5 2 2 3 1
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3. More molecular shapes…
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4. What is the molecular geometry of C2H4?
Determine the shape each carbon atom
2 trigonal planar connected with a double bond
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5. Polar Molecules Must contain at least one polar bond
Must contain at least one polar bond
Are shaped so that there is a (+) and a (-) end
Example of a polar molecule
H2O
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6. Non-Polar Molecules Contain only non-polar bonds
Contain polar bonds, but has no charged ends
example of a non-polar molecule
CCl4
C en.=2.5
Cl en.= 3.5
= 1.0 (polar bond)
Episode 503

7. Intermolecular Forces
Force of attraction between molecules
Are weaker than covalent and ionic bonds
3 types
Dipole to dipole
Force of attraction between the positive end of one molecule and negative end of a molecule
The stronger of all intermolecular forces
Hydrogen bonding (special type of dipole)
Occurs in molecules with H-F, H-O, and H-N bonds
Large positive charge of H is attracted to an unshared pair of electrons on a neighboring molecule
London Dispersion Forces
Weak intermolecular forces resulting from constant motion of electrons
The only type of intermolecular force between non-polar molecules (actual observed in all molecules)
Episode 503