When a strong base is dissolved in water, it undergoes ionization and dissociates into its constituent ions. The base donates electrons to water molecules, resulting in the formation of hydroxide ions (OH-) and the conjugate acid of the base.

For example, when sodium hydroxide (NaOH), a strong base, is dissolved in water, it undergoes the following ionization reaction:

```

NaOH (s) → Na+ (aq) + OH- (aq)

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In this reaction, sodium hydroxide dissociates into sodium ions (Na+) and hydroxide ions (OH-). The hydroxide ions produced by strong bases contribute to the alkalinity or basicity of the solution.