Non-metals include hydrogen, carbon, nitrogen, oxygen, phosphorous, selenium and sulfur. The non-metals consist of elements in groups 14, 15 and 16 on the periodic table of elements. They include both solids and gases.
Non-metals differ from metals in their physical and chemical properties. Non-metals are brittle and not ductile materials. They conduct heat and electricity poorly. They lack luster and do not exhibit any reflective properties. In addition, they have low densities. In contrast, metals are not brittle but malleable and can be molded into various sheets. They are good conductors of electricity and heat and are ductile, meaning they can be formed into a thin wire. They possess luster and reflective qualities. While non-metals are solids, liquids and gases at room temperature, metals are only solids at room temperature. In terms of chemical properties, non-metals have four to eight electrons in their outer shell. They are able to gain or share electrons easily. They form acidic oxides and are good oxidizing agents. Their electronegativities are higher than those of metals. Metals have one to three electrons in their outer shell. They readily lose valence electrons and form oxides that are basic. They are good reducing agents and have low electronegativiteis in comparison to non-metals.