highland science department molecule shapes why do these molecules have such different shapes?
TRANSCRIPT
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