Explanation: Uranium- 238 is an unstable isotope of uranium. It is one of the most effective isotope used for radioactive dating in order to determine the age of a rock that is about billions of years old. It contains an unstable nucleus that undergoes continuous decay, until it reaches a stable environment. It has a half life of approximately 4.5 billion years and majority of the uranium that are present on earth at present are all uranium- 238 and they are constantly decaying. When uranium completely decays, it then gets converted into lead, which is a stable element.
The most common radioactive method used to date rocks is Uranium-Lead dating method.
