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# Chemical formula

Chemical formula of hydrogen peroxide, H2O2
Chemical formula of methane, CH4
Chemical formula of glucose showing the bonds between atoms

A chemical formula (or molecular formula) is one way chemists describe a molecule. The formula says what atoms, and how many of each type, are in the molecule. Sometimes the formula shows how the atoms are linked, and sometimes the formula shows how the atoms are arranged in space.

The letter shows what chemical element each atom is. The subscript shows the number of each type of atom. For example, hydrogen peroxide has the formula H2O2. Methane has one carbon (C) atom and four hydrogen atoms; the chemical formula is CH4. The sugar molecule glucose has six carbon atoms, twelve hydrogen atoms and six oxygen atoms, so its chemical formula is C6H12O6.

Chemical formulas are used in chemical equations to describe chemical reactions.

The 19th-century Swedish chemist Jöns Jacob Berzelius worked out this system for writing chemical formulas.

      . ASIN B000ZI5Z2K.