Whenever acts as a conjunction connecting a time condition to a main action. It carries two related meanings in everyday English. First, it describes repeated routines, meaning every time that an event occurs. Second, it offers flexible permission for a single event, meaning at any time that suits someone.
In contrast, the two-word phrase when ever splits into the question word when and the intensifier ever. In that pattern, ever adds strong emotion such as surprise, curiosity, or frustration. It never establishes a schedule condition or flexible invitation.
You can stop by the cafe whenever you finish your morning classes.