Each radioactive isotope decays by a fixed amount, and this amount is called the half-life.The half-life is the time required for half of the original sample of radioactive nuclei to decay.It also allows the estimation of the age of geological samples using the decay of long lived nuclides.All radioactive decays follow first order kinetics. Radiocarbon decays slowly in a living organism, and the amount lost is continually replenished as long as the organism takes in air or food.Once the organism dies, however, it ceases to absorb carbon-14, so that the amount of the radiocarbon in its tissues steadily decreases.They have the same ratio of carbon-14 to carbon-12 as the atmosphere, and this same ratio is then carried up the food chain all the way to apex predators, like sharks.
A form of radiometric dating used to determine the age of organic remains in ancient objects, such as archaeological specimens, on the basis of the half-life of carbon-14 and a comparison between the ratio of carbon-12 to carbon-14 in a sample of the remains to the known ratio in living organisms. A technique for measuring the age of organic remains based on the rate of decay of carbon 14.
This is called Therefore the characteristic property of the radioisotope, namely its radioactivity can act as a tag or label, which permits the fate of the element or its compound containing this element to be traced through a series of chemical or physical changes.
Some of the application of tracer techniques are discussed below.
Because the cosmic ray bombardment is fairly constant, there’s a near-constant level of carbon-14 to carbon-12 ratio in Earth’s atmosphere.
Organisms at the base of the food chain that photosynthesize – for example, plants and algae – use the carbon in Earth’s atmosphere.