Final answer:
In a system with 4 atoms and 1 lone pair, there are a total of 5 electron groups.
Step-by-step explanation:
The total number of electron groups in a system with 4 atoms and 1 lone pair can be determined by counting the number of bonding pairs (single, double, triple bonds) and lone pairs. Each bond or lone pair counts as one electron group. In this case, we have 4 atoms and 1 lone pair, which means we have 4 bonding pairs and 1 lone pair. Adding these up gives us a total of 5 electron groups.