MOLECULAR GEOMETRY
Molecular Geometry- the
study of the shape of the
molecule.
Things that we need to know about molecules:
1.Molecular shapes are symmetrical-The bonds
and atoms are arranged in regular patterns,
with equal distances separating the atoms
that are not bonded to each other.
2.The VALENCE –SHELL-ELECTRON PAIR REPULSION
THEORY (VSEPR)- states that in a small
molecule, the pairs of shared electron are
arranged as far apart from each other as
possible .
3. Bond angles are formed between two
adjacent bonds. The bond angles are
geometric.
The Five Common Geometric Molecular Shapes
are:
1.Linear- atoms are connected in straight
line. All molecules that contain only 2
atoms are linear. Many molecules that
contains 3 atoms are also linear.
- Bond angle in Linear Molecule is 1800
Example: Carbon dioxide( CO2 )
2. Trigonal Planar- Trigonal means
triangular, and planar means flat. Therefore,
a molecule that is trigonal planar has a
triangular shape. In general a trigonal
planar molecule has a central atom that is
bonded to three other atoms, and the central
atom has no unshared pair of electrons.
- Bond angle is 1200
Example: Boron trichloride ( BCl3)
3. Tetrahedral- the prefix tetra- means four
and the suffix hedral- means to surface. The
tetrahedron is a shape that has four
surfaces.
-Tetrahedron has four sides shapes like a
triangle .
-Angle bond is 109.50
Example: Methane (CH4)
4. Pyramidal- have a central atom that is
bonded to 3 other atoms and has unshared pair
of valence electrons. The unshared pair
exerts a greater repulsive force because they
are held by one atom’s nucleus only.
Example : Ammonia (NH4) -Angle bond is 1070
5. Bent- A bent molecule is a shape like
letter V.
Example : Water (H20) -Angle bond is 1050