For geological purposes, this is taken as one year.
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. 1979, 1986 © Harper Collins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Cite This Source (rā'dē-ō-mět'rĭk) A method for determining the age of an object based on the concentration of a particular radioactive isotope contained within it.
If you could watch a single atom of a radioactive isotope, U-238, for example, you wouldn’t be able to predict when that particular atom might decay.
This decay is an example of an exponential decay, shown in the figure below.
Knowing about half-lives is important because it enables you to determine when a sample of radioactive material is safe to handle.
The nucleus contains protons (tiny particles each with a single positive electric charge) and neutrons (particles without any electric charge).
Orbiting around the nucleus are electrons (tiny particles each with a single electric charge).
Each chemical element, such as carbon and oxygen, consists of atoms unique to it.