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Radioactive isotopes used in dating fossils

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Recall that atoms are the basic building blocks of matter.

Atoms are made up of much smaller particles called protons, neutrons, and electrons.

An ice core is a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica or Greenland or from high mountain glaciers elsewhere.

Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper, and an ice core contains ice formed over a range of years.

Radioactive elements, either of natural origin or created by nuclear testing, can be used to date the layers of ice in the cores.

Some volcanic events which were sufficiently powerful to have distributed material around the globe leave a signature in the ice which can be detected in many different cores, allowing synchronization of the time scales between two different locations.

Isotopes participate in the same chemical reactions but often at differing rates.

When isotopes are to be designated specifically, the chemical symbol is expanded to identify the mass (for example, C is not stable.

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Carbon-14 is most abundant in atmospheric carbon dioxide because it is constantly being produced by collisions between nitrogen atoms and cosmic rays at the upper limits of the atmosphere.Ninety-nine percent of these also contain six neutrons.The 6 proton 6 neutron atoms are said to have a mass of 12 and are referred to as "carbon-12." The nuclei of the remaining one percent of carbon atoms contain not six but either seven or eight neutrons in addition to the standard six protons.Note that, contrary to a popular misconception, carbon dating is not used to date rocks at millions of years old.Before we get into the details of how radiometric dating methods are used, we need to review some preliminary concepts from chemistry.The release of radiation is also a random event and overtime the activity of the radioactive material decreases.