Atoms are made up of much smaller particles called protons, neutrons, and electrons.
Protons and neutrons make up the center (nucleus) of the atom, and electrons form shells around the nucleus.
One is for potentially dating fossils (once-living things) using carbon-14 dating, and the other is for dating rocks and the age of the earth using uranium, potassium and other radioactive atoms.
The atomic number corresponds to the number of protons in an atom.
There are two main applications for radiometric dating.The number of protons in the nucleus of an atom determines the element.For example, all carbon atoms have 6 protons, all atoms of nitrogen have 7 protons, and all oxygen atoms have 8 protons.By dating these surrounding layers, they can figure out the youngest and oldest that the fossil might be; this is known as "bracketing" the age of the sedimentary layer in which the fossils occur.Teach your students about absolute dating: Determining age of rocks and fossils, a classroom activity for grades 9-12.