Chemical formula

A chemical formula is a way that 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. These are called chemical symbols and they are one or two letters long. The subscript shows the number of each type of atom. For example, 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.

 Reading and writing formulas 
Chemical formulas are another way to represent the number of atoms. Chemical formulas are used to represent kinds of atoms in a combination. Chemical formulas use subscripts to tell how many of each atom are present in a combination. Subscripts are small numbers to the lower right of a symbol. They represent the number of atoms of that element in the equation. Before writing Chemical formulas, write down the symbol of each atom present in your equation. Writing chemical formula is a way of informing the chemical figure. It is most easily found in the periodic table. The periodic table is a chart of all well-known parts. Use the periodic table to reference the figure that cannot be remembered.

 Kinds of formulas 
A molecular formula is the most common kind: it says the number of atoms in a molecule. An empirical formula instead shows the ratio between atoms of different elements. For example, the empirical formula of glucose is CH2O, because there are the same number of carbon and oxygen atoms, and twice that number of hydrogen atoms. The empirical formula is used for salts, which make large networks instead of separate molecules.

 Related pages 
Chemical equation

 References 

Category:Chemical nomenclature
Category:Notation