Final answer:
Aminopenicillins like ampicillin and amoxicillin have greater activity against Gram-negative bacteria compared to Penicillin G. Amoxicillin has better oral absorption due to its increased acid stability.
Step-by-step explanation:
The agents that are extended-spectrum penicillins or aminopenicillins, which have a greater activity for Gram-negative bacteria than Penicillin G, include ampicillin and amoxicillin. These aminopenicillins have an added amino group that increases their spectrum of activity against more gram-negative pathogens. Among these, amoxicillin has better oral absorption because the addition of a hydroxyl group (-OH) to its structure increases its acid stability, allowing it to withstand the acidic pH of the stomach.