The modern atomic theory, which states that all matter is composed of atoms, is chemistry. Atoms are composed of protons, neutrons, and electrons. Every element has its own atomic number, which is equal to the number of protons in its nucleus. The smallest piece of an element maintains the identity of that element is called an atom and they are extremely small. It would take fifty million atoms in a row to make a line that is 1 cm long. At the end of the period a printed sentence has several million atoms in it. Atoms are so small and difficult to believe that all matter is made from atoms. It play a fundamental role in chemistry is formalized by the modern atomic theory.
