Ionic reactions show only the ions that react and the products that form.
Lets take the
reaction between solutions of silver nitrate and sodium chloride. A white
precipitate of silver chloride forms.(Click
to see a 120kb movie).
But the Na+ and NO3- ions do not take part in the reaction. There are free sodium and nitrate ions floating in solution before and after the reaction. The ions that do not take part in the reaction are called spectator ions.
The only ions reacting to form a new product are the Ag+ and Cl- ions. The new product formed is solid silver chloride (AgCl).
So the balanced ionic equation for this reaction is given below
+ Cl-(aq) => AgCl(s)
Click to see an animated explanation of the process above.
Example . Write the ionic equation
for the reaction that occurs between solutions of magnesium sulfate and
MgSO4(aq) + Na2S(aq) => MgS(s) + Na2SO4(aq)
Mg2+(aq) + SO42-(aq) + 2Na+(aq) + S2-(aq) => MgS(s) + 2Na+(aq) + SO42-(aq)
Step 3 Delete from the equation the spectator ions.to obtain the balanced ionic equation for this reaction.
Mg2+(aq) + S2-(aq) => MgS(s)
Write ionic equations for the following
sulfate and sodium carbonate (Solution)
Click to see the chart of common ions