Radiometric dating oldest rock
This happens at any time when addition of the fleeting "weak nuclear force" to the ever-present electrostatic repulsion exceeds the binding energy required to hold the nucleus together.
Very careful measurements in laboratories, made on VERY LARGE numbers of U-235 atoms, have shown that each of the atoms has a chance of decaying during about 704,000,000 years.
For example, U-235 is an unstable isotope of uranium that has 92 protons and 143 neutrons in the nucl eus of each atom.
Some elements have forms (called isotopes) with unstable atomic nuclei that have a tendency to change, or decay.In other words, during 704 million years, half the U-235 atoms that existed at the beginning of that time will decay to Pb-207. Many elements have some isotopes that are unstable, essentially because they have too many neutrons to be balanced by the number of protons in the nucleus.Each of these unstable isotopes has its own characteristic half life. Students not only want to know how old a fossil is, but they want to know how that age was determined.Some very straightforward principles are used to determine the age of fossils.