What are the Properties of Simple
(compare these with giant molecules and ionic compounds).
When non-metals react with non-metals
a covalently bonded molecule is formed.
bonds are strong but only exist
between the atoms of the molecule.
The force of attraction between molecules
(called the intermolecular force)
is very weak (compare this with ionic bonding).
The picture below shows the forces of attraction
between two molecules of oxygen gas.
force between molecules
means that very little energy
is needed to separate them. Many molecular compounds
are liquid or gas at room temperature.
They have low melting and boiling points.
Note that when a molecular compound melts or boils,
molecules separate from each other
but the covalent bond between the atoms of the molecule
does not break. The molecule is the same molecule
in the solid, liquid or gas state.
If the covalent bond breaks,
the molecule is said to decompose (split up!).
Molecules do not have
a charge (no ions) because
electrons are shared between atoms to form a covalent bond.
Molecular substances will therefore not conduct electricity
(with the exception of graphite which is a giant molecule).
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