1. Plural of protoxide; chemical compounds formed when an element combines with oxygen in its lowest proportion, or oxides containing the smallest amount of oxygen relative to the metal.
Usage: chemistry; technical; dated term; modern chemistry prefers systematic nomenclature

Examples

• Iron protoxides contain less oxygen than iron peroxides.
• The chemist studied various protoxides to understand oxidation states.
• Protoxides were historically important in early chemical classification systems.
• Copper protoxides differ significantly in their properties from higher oxides.
• The formation of protoxides occurs under specific oxygen-limited conditions.