Radiometric dating parent to daughter ratios
If, however, the rock is subjected to intense heat or pressure, some of the parent or daughter isotopes may be driven off.Therefore, scientists perform radiometric dating only on rocks or minerals that have remained closed systems.The discovery gave scientists a tool for dating rocks that contain radioactive elements.Many elements have naturally occurring isotopes, varieties of the element that have different numbers of neutrons in the nucleus.(The nucleus of an atom is made up of protons and neutrons.) For example, the element carbon, which always has six protons in its nucleus, has three isotopes: one with six neutrons in the nucleus, one with seven, and one with eight.Some isotopes are stable, but some are unstable or radioactive.Concep Test questions by David Mc Connell , David Steer , Walter Borowski, Jeffrey Dick, Annabelle Foos, Jeffrey Knott, Alvin Konigsberg, Michelle Malone, Heidi Mc Grew, Kathie Owens, and Stephen Van Horn The half-life of a radioactive isotope is 500 million years. Scientists testing a rock sample discover that the sample contains three times as many daughter isotopes as parent isotopes.
These rates are usually expressed as the isotope's half-life--that is, the time it takes for one-half of the parent isotopes to decay.Scientists determined the Earth's age using a technique called radiometric dating.Radiometric dating is based upon the fact that some forms of chemical elements are radioactive, which was discovered in 1896 by Henri Becquerel and his assistants, Marie and Pierre Curie.Radiometric dating works best on igneous rocks, which are formed from the cooling of molten rock, or magma.As magma cools, radioactive parent isotopes are separated from previously formed daughter isotopes by the crystallization process.Note that at time 0, the time of the mineral's formation, the crystal contains only parent atoms.At time 1, 50% of the parent atoms remain; at time 2, only 25% remain, and so on.Over time, radioactive isotopes change into stable isotopes by a process known as radioactive decay.Some radioactive parent isotopes decay almost instantaneously into their stable daughter isotopes; others take billions of years.Recently, rocks over 3.96 billion years old have been dated from northern Canada, Wyoming, and China.The ages of these oldest rocks still don't tell us how old the Earth is, but they do establish a minimum age.