Answer to Question #87139 in Physical Chemistry for Suhasree

Question

Explain the principles of radioactive dating?

Answer 1

Radio isotope or radiometric dating is a method for determining the age of various objects

that contain a radioactive isotope. Based on the determination of how much of this isotope had

time to disintegrate during the life of the sample. From this value, knowing the half-life of a given

isotope, one can calculate the age of the sample.

Different isotopes of different elements are used in different methods of radioisotope

dating. Since they differ greatly in chemical properties (and, therefore, in content in various

geological and biological materials and in behavior in geochemical cycles), as well as in half-life,

the range of applicability of different methods varies. Each method is applicable only to certain

materials and a certain interval of ages. The most well-known methods of radioisotope dating are

radiocarbon, potassium-argon (modification-argon-argon), potassium-calcium, uranium-lead, and

thorium-lead methods. Also to determine the geological age of rocks are widely used helium

(based on the accumulation of helium-4 from alpha-active natural isotopes), rubidium-strontium,

samarium-neodymium, rhenium-osmium, lutetium-hafnium methods. In addition, non-equilibrium

dating methods are used, based on the violation of isotopic equilibrium in natural radioactive

series, in particular, ionium, ion-protactinium, uranium-isotope methods and the lead-210

method. There are also methods based on the accumulation of changes in the physical properties

of a mineral under the action of irradiation: the track dating method and the thermoluminescent

method.