Final answer:
The missing term is 'carbon', which refers to carbon dioxide, a gaseous sterilant used in conjunction with ethylene oxide and propylene oxide for the sterilization of heat-sensitive items and medical equipment.
Step-by-step explanation:
The missing term in the sentence 'Ethylene oxide, propylene oxide, and ____ dioxide are commonly used as gaseous sterilants or disinfectants.' is carbon, referring to carbon dioxide (CO₂). Both ethylene oxide and propylene oxide are epoxy compounds used as sterilizing agents. Ethylene oxide is a potent sterilant that operates through an SN2 mechanism with amino (-NH₂) and sulfhydryl (-SH) groups, altering biochemicals and leading to the death of microorganisms. It is commonly used for sterilizing items that are sensitive to heat, such as medical devices and packaged materials, due to its high penetrative ability. However, it is important to note that ethylene oxide is carcinogenic and explosive, which necessitates careful handling and usage. Carbon dioxide, in its supercritical form, is also an effective, non-toxic, and non-reactive sterilant. It is used to sterilize medical devices, implants, and transplanted tissues because it can easily permeate materials and lower intracellular pH, leading to sterilization. Hydrogen peroxide is another commonly used peroxygen that serves as a disinfectant and antiseptic. It is effective against a broad spectrum of microorganisms, including bacteria, yeasts, and spores, though higher concentrations and longer contact times are sometimes required for sporicidal action.