Isotones

atoms of different chemical elements with the same number of neutrons in their nuclei. The following are examples of isotones: the atoms and , whose nuclei contain three neutrons each. Among these isotones, ⁵He decays almost instantaneously, ⁶Li is stable, and ⁷Be and ⁸B are radioactive—they have half-lives of 43 days and 0.8 sec, respectively.