Highland Science Department Molecule Shapes Why do these molecules have such different shapes?

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