Physical Constants Astro Constants Particle Data Unit Conversion Periodic Tables Materials Safety Nobel Info Exact Time Fund. All elements, except the most common form of hydrogen, contain neutrons to help hold the positively charged protons in their nucleus together. Neutrons add to the strong nuclear force without adding to the mutually repulsive electrical force of the protons.
Every element can exist in different forms, called isotopes.
Each isotope of an element contains the same number of protons but different numbers of neutrons. While some isotopes are stable and others are not, they are ALL called isotopes just as all siblings in a family are brothers or sisters. Carbon, for example, has a stable nucleus when its 6 protons are joined by 6 neutrons. When you get to elements with a larger number of protons in their nucleus, the ratio of neutrons to protons increases. Uranium, for example, has the largest naturally occurring nucleus with 92 protons and over 140 neutrons.