gcsescience.com 31 gcsescience.com
Properties of Molecules.
When a non-metal reacts with
a non-metal
they form a covalently
bonded molecule.
Covalent
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.
The weak
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
the electrons are
shared between atoms to form a
covalent bond.
Molecular substances will therefore
not conduct electricity
(with the exception of graphite).
gcsescience.com Contents The Periodic Table Index Quizzes gcsescience.com
Copyright © 2008 Dr. Colin France. All Rights Reserved.
