Chemical equations contd.

Last time we saw how to make compounds using elements and their valence. Here are some exercises for you to try

Mg +O(2)=?
Na+Cl(2)=?
HCl+ Zn=?
Post answers in the comments.

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.