Answer:
Elements that are gases, or are brittle solids, and are poor conductors at room temperature are nonmetals
Explanation:
Elements that are usually gases or solids and are poor conductors at room temperature.
Metals not an option, because they aren't gasses. Most metals have a characteristic lustre and are good conductors of heat and electricity, at room temperature.
Metalloids are unique because they have properties of both metals and non-metals. But, most metalloids are poor conductors of heat and electricity. Metalloids aren't an option either.
Every element has isotopes. They can be gasses, solids,.. Can be good or bad conductors. Isotopes isn't an option either.
Solid nonmetals are not malleable or ductile, but brittle or powdery. Nonmetals are poor conductors of heat and electricity, because electrons are not free to move.
Elements that are gases, or are brittle solids, and are poor conductors at room temperature are nonmetals
