Net Ionic Equations
Introduced| English | Meaning |
|---|---|
| net ionic equation/net aɪˈɒnɪk ɪˈkweɪʒn/ | A reaction equation showing only the species that change, omitting spectator ions. |
| spectator ions/spekˈteɪtə ˈaɪɒnz/ | Ions present in a reaction mixture that undergo no net chemical change. |
Cutting a reaction to its core
- Mix two clear solutions and a solid suddenly appears.
- But most of the dissolved ions just drift by, unchanged.
- Only a few actually take part in the change.
- We can strip an equation down to just those.
Three ways to write it
- The molecular equation shows whole compounds.
- The complete ionic equation splits every dissolved ionic compound into ions.
- The net ionic equation 净离子方程式 keeps only the ions that react.
Mixing two solutions can form an insoluble precipitate
Which species is split into ions in the complete ionic equation?
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Only dissolved (aqueous) ionic compounds are written as ions.
Spectator ions cancel
- Spectator ions 旁观离子 appear unchanged on both sides.
- Cancel them, just like identical terms in algebra.
- What remains is the net ionic equation.
A spectator ion is one that...
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Spectators do not change, so they cancel out.
After cancelling spectator ions, what remains is the ____ ionic equation.
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The leftover reacting ions form the net ionic equation.
The real change
- The net ionic equation shows only the species that actually change.
- For a precipitate, it is the two ions that join to form the solid.
- It captures the true chemistry, stripped of clutter.
Write a net ionic equation
Strip a reaction down to the ions that actually react.
A solid precipitate is written as separate ions in the net ionic equation.
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Only aqueous ions split; a solid stays as one whole formula.
A net ionic equation only needs to balance atoms, not charge.
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False. Both mass and charge are conserved, so a correct net ionic equation balances atoms and total charge.
$\text{AgNO}_3 + \text{NaCl} \to \text{AgCl} + \text{NaNO}_3$.
- $\text{Na}^+$ and $\text{NO}_3^-$ are spectators, so cancel them.
- Net ionic equation: $\text{Ag}^+ + \text{Cl}^- \to \text{AgCl}$.
For $\text{Ag}^+ + \text{NO}_3^- + \text{Na}^+ + \text{Cl}^- \to \text{AgCl} + \text{Na}^+ + \text{NO}_3^-$, the net ionic equation is...
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$\text{Na}^+$ and $\text{NO}_3^-$ are spectators; only Ag and Cl react.
Only aqueous (dissolved) ionic compounds split into ions — solids, liquids, and gases stay whole. Spectator ions are identical on both sides, so cancel only those. And the net ionic equation must still balance in both atoms and charge.
A net ionic equation strips a reaction to the ions that actually change. Split aqueous ionic compounds into ions, cancel the spectator ions that are identical on both sides, and keep the rest — like $\text{Ag}^+ + \text{Cl}^- \to \text{AgCl}$. The result must balance atoms and charge.