Final answer:
The term 'benign solvents' is not one of the 12 green chemistry principles; however, the use of safer solvents is included. Atom economy is indeed among the principles and focuses on the efficient use of reactants in a chemical synthesis.
Step-by-step explanation:
The principle that is not among the 12 green chemistry principles is 'benign solvents.' While using safer solvents is one of the principles, the term 'benign solvents' specifically is not listed. The 12 principles of green chemistry include designing syntheses and products to be less hazardous (less hazardous chemical syntheses), using renewable raw materials (renewable feedstocks), and maximizing atom economy, to name a few. Atom economy is a key principle, which is about maximizing the efficiency of a chemical process, measuring the mass percentage of reactants converted into the final product. The green chemistry principle related to solvents advises the use of safer alternatives and to enhance energy efficiency, thereby not directly referencing 'benign' but implicitly suggesting solvents that are less toxic and environmentally damaging.