Here's a breakdown:

* Definition: An Arrhenius base is a substance that, when dissolved in water, produces hydroxide ions (OH-).

* Mechanism: Arrhenius bases typically dissociate in water to release hydroxide ions. This process is often represented by a chemical equation. For example, sodium hydroxide (NaOH) dissociates in water to form sodium ions (Na+) and hydroxide ions (OH-):

```

NaOH(s) → Na+(aq) + OH-(aq)

```

* Examples: Common examples of Arrhenius bases include:

* Hydroxides: Sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2).

* Some metal oxides: These react with water to form hydroxides. For example, calcium oxide (CaO) reacts with water to form calcium hydroxide (Ca(OH)2).

Key points to remember:

* Aqueous solution: Arrhenius bases must be dissolved in water to show their characteristic behavior.

* Hydroxide ions: The production of hydroxide ions is the defining feature of an Arrhenius base.

* Limited scope: The Arrhenius definition of a base is limited in its scope as it only applies to substances that produce hydroxide ions in water. Other definitions, like the Brønsted-Lowry definition, are more comprehensive.