Represented by molecular formula, chemical name, common name or brand name. In chemical experiments, raw material solutions can be represented by molecular formula, chemical name, common name or brand name. Molecular formula (molecular formula) is a chemical composition formula that uses element symbols to express the composition and relative molecular mass of pure substances (elements, compounds) molecules. Some substances are indeed composed of molecules. The atoms in the molecules are connected by valent bonds, and the molecules are connected by van der Waals forces or hydrogen bonds. These substances have molecular formulas.