According to Arrhenius, acids and bases are defined by what they produce when dissolved in water:

Acids:

* Produce hydrogen ions (H+) when dissolved in water.

* This means they increase the concentration of H+ ions in the solution.

Bases:

* Produce hydroxide ions (OH-) when dissolved in water.

* This means they increase the concentration of OH- ions in the solution.

Here are some examples:

Acids:

* Hydrochloric acid (HCl): HCl → H+ + Cl-

* Nitric acid (HNO3): HNO3 → H+ + NO3-

* Sulfuric acid (H2SO4): H2SO4 → 2H+ + SO42-

Bases:

* Sodium hydroxide (NaOH): NaOH → Na+ + OH-

* Potassium hydroxide (KOH): KOH → K+ + OH-

* Calcium hydroxide (Ca(OH)2): Ca(OH)2 → Ca2+ + 2OH-

Key points to remember about Arrhenius theory:

* It focuses on the behavior of acids and bases in aqueous solutions.

* It's a simple and useful model for understanding the properties of acids and bases, but it has limitations.

* It doesn't explain the behavior of substances that act as acids or bases in non-aqueous solvents.

Let me know if you would like to know more about other acid-base theories like Brønsted-Lowry or Lewis!