How to Write and Balance Net Ionic Equations

Writing and balancing net ionic equations can be challenging but if you carefully follow the correct steps you will be successful. In many ways it is just an extension of balancing molecular (regular) equations except with net ionic equations we take into account the charge on ions.

The general steps for writing net ionic equations are:

1. Write the balanced molecular equation.
2. Write the state (s, l, g, aq) for each substance.
3. Split strong electrolytes into ions (the complete ionic equation).
4. Cross out the spectator ions on both sides of complete ionic equation.
5. Write the remaining substances as the net ionic equation.

-----
Molecular Equation: The equation we are given without anything broken apart into ions.

Total or Complete: all strong electrolytes are broken apart into ions. We don’t break apart solids, liquids, gases, or weak electrolyte.

Net Ionic: What is left after we cancel out the ions that appear on both sides of the Complete Ionic Equation. These are called Spectator Ions.
-----

Note that not all equations are net ionic equations. For example, H2 + O2 = H2O is not a net ionic equation. The H2 and O2 are gases and don’t split apart into ions. Water is a liquid that stays bonded and doesn’t dissociate into ions (actually it does a little bit, and this is important, but not something we consider in writing and balancing net ionic equations).