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Chemical Formula

The atomic composition of a water molecule can be described either in words or by its chemical formula.

In words:
Each molecule of water contains two atoms of hydrogen and one atom of oxygen chemically combined with each other.

By formula:
H2O

Obviously, the chemical formula is a shorter way of describing the atomic composition of the water molecule.
The chemical formula of a molecule shows the number and kinds of atoms contained in it. The chemical formula of a molecule of an element is denoted by the chemical symbol of the element and a subscript showing the number of atoms in the molecule. For example, H2 denotes a molecule of hydrogen which consists of 2 hydrogen atoms.

 

The same method is used in representing the chemical formulae of compounds. There are atleast two chemical symbols in the formula of a compound because each molecule of compound is made of two or more different types of atoms. When more than 1 atom is present, the number of atoms is given by a subscript. When no subscript is written, we assume that the number of atom is one.

Related atomic learning topics:

What is an atom?

Molecule

Key Points.

 
Molecular formula - find molecular formula - how to balance chemical equations