The atom is the smallest unit on Earth. It is the basic component of any type of matter. It cannot be broken down or sectioned. Protons, neutrons and electrons make up the subatomic particles of an atom. The three subatomic particles determine the overall charge of an atom, the chemical characteristics it can possess and its physical properties.

John Dalton was the first to show that matter consisted of smaller particles. Further research conducted by J.J. Thomson provided evidence of electrons and the model of the atom. Since then, the atom was known as the smallest particle on earth. The atom held the title of the smallest particle on Earth for many years. Upon the discovery of protons, neutrons and electrons, the atom’s title changed from smallest particle to smallest unit on Earth.

Located within the nucleus of the atom, a proton has a relatively larger mass than that of an electron but slightly smaller than that of a neutron. A proton will always have at least one positive charge. The proton is responsible for the atom's atomic number. The positive proton charge balances out the negative charge exhibited by the electrons. The protons share the nucleus of the atom with the neutrons and whether free from or bound, the proton maintains a high degree of stability. The protons are important in differentiating among different atoms because the number of protons of a particular atom is specific to that atom. It also determines the chemical properties that the atom will have.

Neutrons are also located in the atom's nucleus and get their name from their chemical charge, which is neutral. The numbers of neutrons along with the protons in the atom give the overall mass number of the atom. Much heavier than electrons and slightly bigger than protons, the number of neutrons within the nucleus of an atom determines the number of isotopes that a particular atom can form. Neutrons are very stable in their bound form within the atom; however, free neutrons are extremely unstable and undergo decay.

Electrons are the smallest subatomic component of an atom and are very light. Electrons carry a negative charge at all times. They exist within orbital clouds of an atom. An electromagnetic force keeps the electron from leaving the atom’s orbit. The electron orbits the atom so fast it is almost impossible to determine the exact location of an electron at a specific time. They are the only subatomic particle that the atom can either give up or gain another one of during chemical bonding. The negative charge of the electron balance out the positive charge of the proton, which helps to establish an overall neutral charge for the atom.