For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively.
The atomic number of carbon is 6, which means that every carbon atom has 6 protons, so that the neutron numbers of these isotopes are 6, 7 and 8 respectively.
The radiocarbon dating method is based on the fact that radiocarbon is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen.
It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.
Radiometric dating utilizes the decay rates of certain radioactive atoms to date rocks or artifacts.
Uniformitarian geologists consider this form of dating strong evidence that the Earth is billions of years old.
Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons.
The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number.