Atom is the basic unit that makes up all matter. There are different types of atoms, each with its own name, size and mass. These different types of atoms are called elements.
Atoms are made up of three smaller particles called protons, neutrons and electrons. The protons and neutrons are located in the middle of the atom, which is called the nucleus. The nucleus is surrounded by the electrons that are bound to the nucleus by an electromagnetic force. Atoms come together to form molecules or particles; two hydrogen atoms and one oxygen atom combining together to form a water molecule is one such example.
The number of protons, electrons and neutrons determines which element an atom is. Atoms also move faster in gaseous form than in liquid and solid matter, because they are able to move freely about. Atoms move the slowest in solid matter, because they are tightly pack and are only able to vibrate in fix positions.