# Carbon dating and half life calculations

When the animal or plant dies, the carbon-14 nuclei in its tissues decay to nitrogen-14 nuclei by a radioactive process known as beta decay, which releases low-energy electrons (β particles) that can be detected and measured: $\ce \label$ The half-life for this reaction is 5700 ± 30 yr. Comparing the disintegrations per minute per gram of carbon from an archaeological sample with those from a recently living sample enables scientists to estimate the age of the artifact, as illustrated in Example 11.Using this method implicitly assumes that the ratio in the atmosphere is constant, which is not strictly correct.Other methods, such as tree-ring dating, have been used to calibrate the dates obtained by radiocarbon dating, and all radiocarbon dates reported are now corrected for minor changes in the to obtain the elapsed time.

The half-life of a first-order reaction under a given set of reaction conditions is a constant.

In any sample of a given radioactive substance, the number of atoms of the radioactive isotope must decrease with time as their nuclei decay to nuclei of a more stable isotope.

Using Activity is usually measured in disintegrations per second (dps) or disintegrations per minute (dpm).

BEFORE DECAY BEGINS, ALL OF THE MATERIAL IS RADIOACTIVEAFTER ONE HALF LIFE, HALF OF THE SAMPLE REMAINS RADIOACTIVE AND THE OTHER HALF IS STABLEAFTER EACH ADDITIONAL HALF LIFE, HALF OF THE REMAINING RADIOACTIVE MATERIAL DECAYSWe use several radioactive isotopes to find the absolute age of events and objects because we know their half life.

On the cover of your ESRT in the top left box you will find the Radioactive Decay Data for four isotopes which we will focus on.