Qualitative Chemistry

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Ionic Equations
Ions fit together like jigsaws. How many ions needed to form a compound is indicated by the ion's charge or valency. Do this by balacing the charges. If one ions has a 2+ charge, and the other has a 1-, you will need two of the 1- to balance the other.
For example:

Fe²⁺ + I^- —> FeI₂

Mg²⁺ + SO₄^2- —>MgSO₄

Ionic equations are written slightly differently to normal chemical equations you will have come across in the past.

Firstly, the spectator ions (ions that, while present, do not take part in the reaction) are not included in the writing of the equations. (When adding NaOH, Na⁺ is a spectator ion)

Secondly, the ion's charge or valency must be written in the equation. (Mg²⁺)

And lastly, the ion's physical state is also written in the equation in brackets.
The physical state of the ion can be aqueous (aq), this means it is in a solution of water. It can be liquid (l) or gas (g) or, when a precipitate is formed, solid (s).

Here's a sample equation:

Cu²⁺_(aq) + 2OH^-_(aq) —> Cu(OH)_{2 (s)}