The chemical formula of water is H2O. Observe that, water is made of two hydrogen atoms and one oxygen atom. Here, two different elements, Hydrogen and oxygen combine, giving rise to a new substance called water. Such substances, which are made by the combination of two or more kinds of elements are called Compounds.
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1. Atoms are singular
Molecules are 2 or more combined atoms 

2. Atoms are not bonded
Molecules are atoms that are bonded

3. Atoms is some thing which can't be split
Molecule can be divided into many atoms.

4. Atom consists of protons, neutrons and electrons.
Molecule is combination of mixture of atoms like H2O, H2, N2, NaCl, NaK, Etc.
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