mean life
mean life, in radioactivity, average lifetime of all the nuclei of a particular unstable atomic species. This time interval may be thought of as the sum of the lifetimes of all the individual unstable nuclei in a sample, divided by the total number of unstable nuclei present. The mean life of a particular species of unstable nucleus is always 1.443 times longer than its half-life (time interval required for half the unstable nuclei to decay). Lead-209, for example, decays to bismuth-209 with a mean life of 4.69 hours and a half-life of 3.25 hours.
Citation Information
Article Title:
mean life
Website Name:
Encyclopaedia Britannica
Publisher:
Encyclopaedia Britannica, Inc.
Date Published:
16 January 2025
Access Date:
February 22, 2025