Recall that atoms are the basic building blocks of matter.
For example, all carbon atoms have 6 protons, all atoms of nitrogen have 7 protons, and all oxygen atoms have 8 protons.
The number of neutrons in the nucleus can vary in any given type of atom.
Note that, contrary to a popular misconception, carbon dating is not used to date rocks at millions of years old.
Before we get into the details of how radiometric dating methods are used, we need to review some preliminary concepts from chemistry.
Protons and neutrons make up the center (nucleus) of the atom, and electrons form shells around the nucleus.