Chemical Equations.

Today we are going to talk about chemical equations.  Chemical equations are nothing more than representations of chemical reactions (we talked about them earlier) . Lets see what happens when I let an iron nail out in the rain for some time(you think).
That is an example of a chemical change. We need some method yo show what happens that is done by chemical equations.(numbers in brackets are to be put downstairs ok)

Iron+Oxygen=Iron oxide

Fe+O(2)= Fe(2)O(3)
This type of equation is called a skeletel equation I.e
The numbers of atoms on both sides are not equal.
BUT, how do I get this monster?

Fe+O(2)= Fe(2)O(3)
Well before getting into this matter you need to recall about valence.
To combine two elements to make a compound follow this "cross multiplication" process.
First write the two elements ( symbols and valence) on both sides like that:

            (3)               (2)
            Fe.               O
Then exchange the valences.
More about this in the next class.