Final answer:
A negative delta G indicates a spontaneous or exergonic reaction, where energy is released and the reaction is energetically favorable.
Step-by-step explanation:
When delta G is negative, the reaction is known as a spontaneous or exergonic reaction. This means that energy is released during the chemical reaction, and the products have less free energy than the reactants. It is important to understand that the term 'spontaneous' does not imply the reaction happens quickly; it simply means it is energetically favorable and can occur under the given conditions without needing additional energy. For example, rusting of iron is a slow, yet spontaneous process. In contrast, endergonic reactions, where delta G is positive, require an input of energy as they proceed toward products with a higher energy state compared to the reactants.