Atoms are the building blocks of everything. Atoms can form strong bonds with each other, making molecules. Symbols and formulae Letters from the alphabet are used to represent chemical elements. An ...

a pure substance consists only of one element or one compound a mixture consists of two or more different substances, not chemically joined together ...

Deep within giant planets, helium may form stable compounds with other elements, a new study finds — something that was long thought never to happen in nature. Helium is second only to hydrogen as the ...