Chemistry Reference
In-Depth Information
Properties of Ionic Compounds
1.
Their bonds are very strong, which means it takes a relatively
high amount of energy to break them.
2.
They tend to be dull, hard, brittle solids at standard
temperature and pressure.
3.
They usually don't conduct electricity in the solid state, but
they are good conductors in molten or aqueous (solution)
form.
4.
They tend to have high melting and freezing points.
5.
The structure of the crystals that they form depends on both
the size and ratio of the ions that make them up.
Molecular compounds are formed from covalent bonds between atoms.
The major difference between molecular and ionic compounds is that in
molecular compounds, you have smaller discreet units making up the larger
sample. In other words, in a block of ice, solid H
2
O, you have groupings of
3 atoms that “belong” together. The atoms within a particular molecule
share bonds that they do not share with atoms from other molecules. So,
whereas the ionic formula of a salt only gives you the ratio of the elements
in the compound, the molecular formula of a molecular compound actu-
ally indicates the small grouping of atoms that exist as molecules in the
larger sample.
A simplistic, but helpful, analogy is to compare a crystal of an ionic
compound to a large crowd of strangers, where no person in the crowd has
a special relationship with any other member of the crowd. A sample of a
molecular compound could be likened to a large crowd that is made up of
individual couples or families. The people in the families have special rela-
tionships, which make them units within the larger group.
Although there many different molecular compounds, they tend to have
certain similar properties.
Properties of Molecular Compounds
1.
The strength of the bonds that make them up can vary a great
deal.
2.
They tend to be liquids or gases at standard temperature and
pressure.
