A pure substance made from more than one type of element chemically bonded together. Elements bond in fixed ratios and so can be represented by a chemical formula. For example, sodium chloride has the ...

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 ...

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 ...