Radiometric dating how stuff works
They all have six protons since they are carbon, and therefore they are identical chemically.
Anything that dies after the 1940s, when Nuclear bombs, nuclear reactors and open-air nuclear tests started changing things, will be harder to date precisely.If we discover a rock with 75% K-40 and 25% Ar-40, we know it has been solid for 0.625 billion years (half of a half-life).Similarly, If we discover a rock with 50% K-40 and 50% Ar-40, we know it has been solid for 1.25 billion years. Note that we do not need to know how much material was present originally, only the ratios that are present today. There are three naturally occurring isotopes of carbon in the environment: carbon-12, carbon-13, and carbon-14.Note that Carbon Dating uses a different method that I will discuss momentarily .The radioactive material is alway decaying into something, but if the material is in a molten state, the decay products will not stay in place. As soon as a living organism dies, it stops taking in new carbon.
The ratio of carbon-12 to carbon-14 at the moment of death is the same as every other living thing, but the carbon-14 decays and is not replaced.
Carbon-14 dating is a way of determining the age of certain archeological artifacts of a biological origin up to about 50,000 years old.
It is used in dating things such as bone, cloth, wood and plant fibers that were created in the relatively recent past by human activities.
Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).
The use of various radioisotopes allows the dating of biological and geological samples with a high degree of accuracy.
However, the principle of carbon-14 dating applies to other isotopes as well.