Radiometric dating is based on
After emission, it quickly picks up two electrons to balance the two protons, and becomes an electrically neutral helium-4 (He4) atom. When an atom emits a beta particle, a neutron inside the nucleus is transformed to a proton.The mass number doesn't change, but the atomic number goes up by 1.Uranium-238 contains 92 protons and 146 neutrons, while uranium-235 contains 92 protons and 143 neutrons.To keep it short, a nuclide is usually written using the elements abbreviation.The half-life of a radioactive nuclide is defined as the time it takes half of a sample of the element to decay.A mathematical formula can be used to calculate the half-life from the number of breakdowns per second in a sample of the nuclide.
Others have extremely short half-lives, measured in tenths or hundredths of a second.
The decay rate and therefore the half-life are fixed characteristics of a nuclide. Thats the first axiom of radiometric dating techniques: the half-life of a given nuclide is a constant.
(Note that this doesnt mean the half-life of an element is a constant.
Since all atoms of the same element have the same number of protons, different nuclides of an element differ in the number of neutrons they contain.
For example, hydrogen-1 and hydrogen-2 are both nuclides of the element hydrogen, but hydrogen-1's nucleus contains only a proton, while hydrogen-2's nucleus contains a proton and a neutron.