Before you can work a net ionic equation, you must be able to identify mono- & polyatomic ions. You must also be familiar with the rules for solubility. You'll find an overview of these at the end.

Let's look at the equation below:

We'll rewrite this equation as separate ions (ionic form) and we'll use the rules of solubility and our knowledge of strong acids. The rules of solubility state that nitrates are soluble, so lead(II) nitrate dissociate. Hydrochloric acid & nitric acid are both strong acids & will dissociate. Lead(II) chloride is insoluble because all halides, except lead, silver, mercury(I) and copper(I) are soluable. The equation in ionic form looks like this:

Now you can cancel the ions that did not participate in this reaction. You'll see that the nitrate ion and hydrogen ion stayed the same before and after the reaction.

What you have left is the net ionic equation which will show only the participants in the chemical reaction.

When you have worked enough of these problems, you will be able to see the net ionic equation just by looking at the reactants. Let's try it with this reaction:

Let's first examine the ions that are in the solution:

The barium & bromide ions are soluble together. So we have to determine if the sodium ions or the sulfate ions will combine with the barium ions to create an insoluble compound. Since barium ions & sodium ions are both positive, they will repel each other and no compound will will form. But, the sulfate ions & the barium ions can join together to form barium sulfate.

Next we need to consult the rules for solubility and find out if barium sulfate is soluble or not. From the rules we know that sulfates, with the exception of barium, lead, and strontium, are soluble. So the barium sulfate is not soluble. This leaves us with the sodium ions combining with the bromide ions to make sodium bromide, which, upon checking our rules, is soluble. We can now write out our balanced equation:

Write the equation in ionic form:

Cancel out the spectator ions:

What you have left is the net ionic equation:

Common Polyatomic Ions

Rules for Solubility:

1. All compounds of Group I and NH₄⁺ are soluble.
2. All chlorates, nitrates, and acetates are soluble.
3. All compounds of halogens (except fluorine) and metals are soluble, (except lead, mercury(I), & silver).
4. All sulfates are soluble, except strontium, barium, lead, calcium, mercury (I), and silver.
5. Except for rule 1, hydroxides, oxides, carbonates, phosphates, and silicates are insoluble.
6. Sulfides are all insoluble except for calcium, barium, strontium, magnesium, sodium, potassium, and ammonium.