How are fossils dated using relative dating
4) To demonstrate how the rate of radioactive decay and the buildup of the resulting decay product is used in radiometric dating of rocks. (A single watch or clock for the entire class will do.) 6) Piece of paper marked TIME and indicating either 2, 4, 6, 8, or 10 minutes.5) To use radiometric dating and the principles of determining relative age to show how ages of rocks and fossils can be narrowed even if they cannot be dated radiometrically. 2) Large cup or other container in which M & M's can be shaken. 7) 128 small cards or buttons that may be cut from cardboard or construction paper, preferably with a different color on opposite sides, each marked with "U-235" all on one colored side and "Pb-207" on the opposite side that has some contrasting color.
Each of these unstable isotopes has its own characteristic half life.This is a stable condition, and there are no more changes in the atomic nucleus.A nucleus with that number of protons is called lead (chemical symbol Pb). This particular form (isotope) of lead is called Pb-207.Principle of cross-cutting relations: Any geologic feature is younger than anything else that it cuts across.Some elements have forms (called isotopes) with unstable atomic nuclei that have a tendency to change, or decay.In general, with the exception of the single proton that constitutes the nucleus of the most abundant isotope of hydrogen, the number of neutrons must at least equal the number of protons in an atomic nucleus, because electrostatic repulsion prohibits denser packing of protons.
But if there are too many neutrons, the nucleus is potentially unstable and decay may be triggered.
That chance of decay is very small, but it is always present and it never changes.
In other words, the nuclei do not "wear out" or get "tired".
U-235 is the parent isotope of Pb-207, which is the daughter isotope.
Many rocks contain small amounts of unstable isotopes and the daughter isotopes into which they decay.
It wasn't until well into the 20th century that enough information had accumulated about the rate of radioactive decay that the age of rocks and fossils in number of years could be determined through radiometric age dating.