The ratio of calcium formed to argon formed is fixed and known.

If we knew the fraction of a radioactive element still remaining in a mineral, it would be a simple matter to calculate its age by the formula To determine the fraction still remaining, we must know both the amount now present and also the amount present when the mineral was formed.The number of protons in the nucleus of an atom is called its atomic number.The sum of protons plus neutrons is the mass number.As you learned in the previous page, carbon dating uses the half-life of Carbon-14 to find the approximate age of certain objects that are 40,000 years old or younger.In the following section we are going to go more in-depth about carbon dating in order to help you get a better understanding of how it works.