Three natural nuclei have half-lives above one billion years (Potassium 40, uranium-238 and thorium-232) while the half-life of polonium 214, a descendant of the same uranium-238, is only 0,16 millisecond. Half-lives can range from a fraction of a second to billions of years.

It determines how quickly it will decay and for how long we need to worry about its radiations. The вЂhalf-lifeвЂ™ of a radioactive nucleus is one of its main features with the nature of radiations it emits. The two heaviest natural nuclei, thorium 232 and uranium 238, are the solitary black dots in the mauve island. Among even heavier nuclei, we find an island of comparative stability (in mauve), where a group of isotopes have a half-life between the one- and the billion-year mark. A group of very heavy, very unstable nuclei can also be found around the 130 neutron, 85 proton mark. Those nuclei which survive for a fraction of a second, however, (coloured in red) can be found on the borders of the diagram. Along the central line drawn in black, we find the nuclei that are either stable or have a half-live longer than a billion years. This map of nuclei shows the extraordinary range of half-lives that exists in nature.

Half life decay