Three methods of radiometric dating
Different nuclides of the same element can have substantially different half-lives.) billion years old.
So, if we know how much of the nuclide was originally present, and how much there is now, we can easily calculate how long it would take for the missing amount to decay, and therefore how long its been since that particular sample was formed. We must know the original quantity of the parent nuclide in order to date our sample In order to do so, we need a nuclide thats part of a mineral compound. Because theres a basic law of chemistry that says "Chemical processes like those that form minerals cannot distinguish between different nuclides of the same element." They simply cant do it.
Uranium-238 contains 92 protons and 146 neutrons, while uranium-235 contains 92 protons and 143 neutrons.
In alpha decay, the radioactive atom emits an alpha particle.
An alpha particle contains two protons and two neutrons.
Thus, an atom of carbon-14 (C14), atomic number 6, emits a beta particle and becomes an atom of nitrogen-14 (N14), atomic number 7.
A third, very rare type of radioactive decay is called electron absorption.
The half-life of a radioactive nuclide is defined as the time it takes half of a sample of the element to decay.