If we talk about Non-metals meaning: these are the elements with dull appearance and present on the right side of the periodic table. All of these elements have low boiling and melting points. They are also not a good conductor of electricity and gain electrons in chemical reactions. Carbon, oxygen, selenium, sulfur, hydrogen, neon, helium, Krypton, Xenon, and Argon, are all non-metals. Some non-metals like helium and hydrogen make up almost 99 per cent mass of the universe

Difference 101