The net ionic equation for an acid-base neutralization reaction shows the combination of a(n) ion with a hydronium ion to form water molecules.

The net ionic equation for an acid-base neutralization reaction shows the combination of a hydroxide ion (OH-) with a hydronium ion (H3O+) to form water molecules (H2O).

Here are the steps:

1. Write the balanced molecular equation. For example, if we consider the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH), the balanced molecular equation would be: HCl + NaOH -> NaCl + H2O

2. Write the total ionic equation. In this case, all strong electrolytes (compounds that dissociate completely into ions in solution) are written as ions: H+ + Cl- + Na+ + OH- -> Na+ + Cl- + H2O

3. Write the net ionic equation. This is done by cancelling out the spectator ions that appear on both sides of the total ionic equation. In this case, Na+ and Cl- are spectator ions, so the net ionic equation is: H+ + OH- -> H2O

So, the net ionic equation for an acid-base neutralization reaction shows the combination of a hydroxide ion (OH-) with a hydronium ion (H3O+) to form water molecules (H2O).