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Highland Science Department
Molecule Shapes
Why do these molecules have such different shapes?
Highland Science Department
Molecule Shapes
recall: bonding pair: e- pairs involved in bondinglone pair: e- pairs not involved in bonding
Highland Science Department
Molecule Shapes
recall: bonding pair: e- pairs involved in bondinglone pair: e- pairs not involved in bonding
VSEPR Theory: Valence Shell Electron Pair
Repulsion Theory
Highland Science Department
Molecule Shapes
VSEPR Theory: Valence Shell Electron Pair Repulsion Theory
-electron pairs are arranged around atoms so that they are a maximum distance from each other in 3 dimensional space
Highland Science Department
Molecule Shapes
VSEPR Theory: Valence Shell Electron Pair Repulsion Theory
-electron pairs are arranged around atoms so that they are a maximum distance from each other in 3 dimensional space
-from Lewis diagrams we know atoms want a stable octet (4 pairs of electrons)
-shapes come from how many of those are bonding pairs & how many are lone pairs
-double & triple bonds also have an effect
Highland Science Department
Molecule Shapes
Tetrahedral: an atom bonded to four other atoms spaced as far apart as possible will create 109.5o angles
Highland Science Department
Molecule Shapes
Tetrahedral: an atom bonded to four other atoms spaced as far apart as possible will create 109.5o angles
e.g. carbon tetrachloride (CCl4)
in 3-D is
Highland Science Department
Molecule Shapes
Pyramidal: if there are one lone pair and three bonding pairs, the lone pair will exert a repulsion on the bonding pairs, resulting in a pyramidal shape
δ-
δ+
Highland Science Department
Molecule Shapes
Pyramidal: if there are one lone pair and three bonding pairs, the lone pair will exert a repulsion on the bonding pairs, resulting in a pyramidal shape
e.g. ammonia (NH3)δ-
in 3-D is
δ+
Highland Science Department
Molecule Shapes
Bent: two lone pairs will force the bonding pairs towards each other and form a bent shape
lone pairs
bonding pairs
Highland Science Department
Molecule Shapes
Bent: two lone pairs will force the bonding pairs towards each other and form a bent shape
e.g. water (H2O)
δ-
in 3-D is
δ+
Highland Science Department
Molecule Shapes
Linear: double bonding the three atoms removes the lone pairs and makes a linear molecule
Highland Science Department
Molecule Shapes
Linear: double bonding the three atoms removes the lone pairs and makes a linear molecule
e.g. carbon dioxide (CO2)
δ- δ+ δ-
in 3-D is
Highland Science Department
Molecule Shapes
Polarity of Molecules:
Polar Molecule: a molecule with a positive end and a negative end
e.g. water (H2O)δ-
δ+
Highland Science Department
Molecule Shapes
Polarity of Molecules:
Non-Polar Molecule: a molecule where all ends are equally charged
e.g. carbon dioxide (CO2)
δ- δ+ δ-
-each end is equally negative so the overall
molecule is non-polar
Highland Science Department
Molecule Shapes
Intramolecular Forces: forces that hold the atoms in a molecule together
Intermolecular Forces: forces that attract molecules to other molecules
Highland Science Department
Molecule Shapes
Intramolecular
Intermolecular
