An atom itself is made up of three tiny kinds of particles called subatomic particles: protons, neutrons, and electrons. The protons and the neutrons make up the center of the atom called the nucleus and the electrons fly around above the nucleus in a small cloud. The electrons carry a negative charge and the protons carry a positive charge. In a normal atom the number of protons and the number of electrons are equal. Often, but not always, the number of neutrons is the same, too. The number of protons in an atom defines the chemical element to which it belongs, while the number of neutrons determines the isotope of the element.