Here's why:

* Beta-lactams are a broad class of antibiotics that work by inhibiting the synthesis of peptidoglycan, a crucial component of bacterial cell walls.

* Ampicillin is a derivative of penicillin and is classified as a aminopenicillin. This means it has a similar structure and mode of action to penicillin.

Therefore, ampicillin belongs to the beta-lactam family of antimicrobial agents.