Once the half life of an isotope and its decay path are known, it is possible to use the radioactive decay for dating the substance (rock) it belongs to, by measuring the amount of parent and daughter contained in the sample.
An important point is that we must have an idea of how much of the daughter isotope was in the sample before the decay started.
So, Carbon-14 can only measure things up to just over 50,000 years old, great for determining when someone built a wood fire, but not good for determining the age of a meteorite. It occurs whenever an atom has an unbalanced number of protons and neutrons in its nucleus.
When there is a scientific discussion about the age of, say a meteorite or the Earth, the media just talks about the large numbers and not about the dating technique (e.g. On the other hand, when the media talk about "more recent events," ages that are more comprehendible, such as when early Man built a fire or even how old a painting is (or some ancient parchment), then we bring up the dating technique in order to better validate the findings.The amount of time it takes for an unstable isotope to decay is determined statistically by looking at how long it takes for a large number of the same radioactive isotopes to decay to half its original amount.This time is known as the half-life of the radioactive isotope.Both carbon-12 and carbon-13 are stable, but carbon-14 is unstable, which means that there are too many neutrons in the nucleus. As a result, carbon-14 decays by changing one proton into a neutron and becoming a different element, nitrogen-14 (with 7 protons and 7 neutrons in the nucleus).
The isotope originating from the decay (nitrogen-14 in the case of radiocarbon) is called the daughter, while the original radioactive isotope (like carbon-14) is called the parent.On the other hand, the number of neutrons that can be contained in the nucleus can vary.