Shapes of Molecules

Electron pair repulsion theory

The shape of a molecule is determined by the electron pairs surrounding the central atom

Pairs of electrons repel all other electron pairs

Electron pairs move as far apart as possible to minimise repulsion

Central atom has 2 covalent bonds

Linear

180^o

Central atom has 3 covalent bonds

Trigonal planar

120^o

Central atom has 4 covalent bonds

Tetrahedral

109.5^o

Central atom has 5 covalent bonds

Trigonal bipyramidal

90^o 120^o

Central atom has 6 covalent bonds

Octahedral

90^o

Central atom has 2 covalent bonds and one lone pair

Bent

177.5^o

Central atom has 2 bonds and one lone pair

Bent

117.5^o

Central atom has 2 bonds and 2 lone pairs

Bent

104.5^o

Central atom has 3 bonds and one lone pair

Triangular pyramidal

107^o

Central atom has 3 bonds and 2 lone pairs

Trigonal planar

120^o (bond angles not affected)

Central atom has 4 bonds and one lone pair

Trigonal pyramidal

117.5^o 87.5^o

Central atom has 4 bonds and 2 lone pairs

Square planar

90^o

Central atom has 5 bonds and one lone pair

Square pyramid

87.5^o