nonmetal definition chemistry
General Chemistry Dictionary. (metal,metalloid) A nonmetal is a substance that conducts heat and electricity poorly, is brittle or waxy or gaseous, and cannot be hammered into sheets or drawn into wire. Nonmetals gain electrons easily to form anions.About 20% of the known chemical elements are nonmetals.efine: (metal,metalloid) A nonmetal is a substance that conducts heat and electricity poorly, is brittle or waxy or gaseous, and cannot be hammered into sheets or drawn into wire.