Protons and neutrons together are called nucleons, meaning particles that can appear in the atomic nucleus.A nuclide of an element, also called an isotope of an element, is an atom of that element that has a specific number of nucleons.I found several good sources, but none that seemed both complete enough to stand alone and simple enough for a What is radiometric dating?Simply stated, radiometric dating is a way of determining the age of a sample of material using the decay rates of radio-active nuclides to provide a 'clock.' It relies on three basic rules, plus a couple of critical assumptions.

However scientists tested the hypothesis that solar radiation might affect the rate at which radioactive elements decay and found no detectable effect.The latest high-tech equipment permits reliable results to be obtained even with microscopic samples.Radiometric dating is self-checking, because the data (after certain preliminary calculations are made) are fitted to a straight line (an "isochron") by means of standard linear regression methods of statistics.Atoms of radioactive isotopes are unstable and decay over time by shooting off particles at a fixed rate, transmuting the material into a more stable substance.For instance, half the mass of carbon-14, an unstable isotope of carbon, will decay into nitrogen-14 over a period of 5,730 years.