Radiometric age dating formula
Strontium-86 is a stable element that does not undergo radioactive change.In addition, it is not formed as the result of a radioactive decay process.Rubidium-Strontium dating: The nuclide rubidium-87 decays, with a half life of 48.8 billion years, to strontium-87.Strontium-87 is a stable element; it does not undergo further radioactive decay.Therefore the amount of argon formed provides a direct measurement of the amount of potassium-40 present in the specimen when it was originally formed.Because argon is an inert gas, it is not possible that it might have been in the mineral when it was first formed from molten magma.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.
At the same time, the fraction of strontium-87 increases from zero and approaches 100% with increasing number of half-lives.
It has the same number of protons, otherwise it wouldn't be uranium.
The number of protons in the nucleus of an atom is called its atomic number.
(Note that this does not mean that the ratios are the same everywhere on earth.
It merely means that the ratios are the same in the particular magma from which the test sample was later taken.) As strontium-87 forms, its ratio to strontium-86 will increase.