Which element from the table above is an Isotope? How can you tell?

For protons, the number always equals the atomic number of the element. Isotopes are simply specifying the number of neutrons and protons (together called nucleons) in the atom. So, Carbon-12, which has an atomic mass number of 12, has 6 neutrons (12 nucleons - 6 protons = 6 neutrons).

tracks, burrows, eggshells, nests, tooth marks, or gastroliths