Isotope

Strontium Isotope ratios are used in archaeology to track human migration.86Sr abundance is constant, but 87Sr forms through decay of 87Rb in rock. Rock age and initial Rb/Sr ratios vary geographically, making87Sr/86Sr a location tracer. Strontium, weathered from bedrock into groundwater then taken up by flora and fauna, can substitute for Ca in tooth enamel. Enamel only forms during childhood, specifically the early first and second molars mineralize during early childhood; the third molar during late childhood/adolescence. Thus 87Sr/86Sr ratios reveal where individuals grew up. Archaeological samples are precious and scarce; mass spectrometers are ideally suited for measuring isotope ratios in such samples. It was hypothesized that individuals…

unit, or amu. Many elements have multiple isotopes, or versions of atoms, which have the same atomic numbers, but a different atomic mass which changes according to the amount of neutrons in the nucleus. By 1911, the constituents of atoms have been discovered to be known as electrons, protons, and neutrons, but what remain undiscovered was how they were arranged. J.J. Thompson theorized that electrons and protons were evenly distributed in the atom which he called the “Plum Pudding” Model.…

Iridium-192 is a radioactive isotope that’s used daily in a series of world changing ways. It’s a synthetically produced metal, made as a by-product of nickel and copper, and the Iridium-containing ores are found in the U.S.A, Alaska, South Africa and Australia. Used both in the medical and industrial world, this radioisotope is underappreciated for its benefits to society. Though there are some risks, the reward undeniably outweighs them. Iridium-192 has a half-life of approximately 73 days,…

This region is characterized by a steep increase of the annual rainfall (summer rains from July to September) from 150 mm/year at their northern margin to more than 350 mm/year at the southern margin. Groundwater samples were collected by Gröning et al., (1993) and analyzed for H and O isotopes in both areas. Darfur has δ18O, which varies between -10.99 and 4.73‰, while δD ranges between -81.7 and 42‰; Kordofan has δ18O, which varies between -11.26 and 14.57‰, while δD ranges between -80.5 and…

magnesium, for instance, possesses 3 energy levels because of its location in Group 3. 20th Century physicist Niels Bohr developed the following definition of electron shells that continues to be widely accepted today: the arrangement of these subatomic particles in levels according to the amount of energy they have. An electron can move between shells upon gaining or losing energy, but are restricted to orbits of certain energies. As a final note, perhaps the most critical piece of information…

What is radioactive dating? and how does it work? Radioactive, or Radiometric dating is a technique used to determine the age of objects such as rocks or carbon by using the decay rate of radioactive isotopes. It has been used since its invention by Ernest Rutherford in 1905. Radioactive decay itself, is the process by which an unstable atomic nucleus loses energy by emitting radiation. Each radioisotope decays at its own fixed rate and this is measured in half lives. As discussed in Lesson 6,…

Once a living thing dies, the carbon dating process begins. As long as an organism is alive it will continue to take in 14C or radio carbon; however, when it dies, it will stop. Since 14C is radioactive (decays into 14N), the amount of 14C in a dead organism gets less and less over time. Therefore, part of the dating process involves measuring the amount of 14C that remains after some has decayed. Scientists now use a device called AMS (don't know what it stands for) to figure out the ratio of…

Bentley, R. Alexander 2006 Strontium Isotopes from the Earth to the Archaeological Skeleton: A Review. Journal of Archaeological Method and Theory13(3): 138–187. In this article, Bentley provides a review of and explains the various ways in which strontium isotopes are used in archaeology, as well as potential problems with their analysis. He gives a detailed description of what strontium isotopic ratio analysis is, and how these numbers can indicate mobility through life. While a very…

Radiocarbon dating was invented similarly with the discovery of the Dead Sea Scrolls. Furthermore, due to the long duration of time elapse, it was hard to date the time when the scrolls were produced. Although the hot and dry climate of the Dead Sea prevented it from rotting severely, it was still difficult to exclude the containments included in the fragments and scrolls. As a result, the process of processing the samples was intricate. At the first part of the process, the scientists tried to…

Ashley-Ann Burnett October 4, 2015 Lab #3: Acids, Bases & pH SLS43-14/7-8 Pre-Lab Questions: 1) An isotope is an atom with a different atomic weight due to changes in the number of neutrons in the nucleus. Some examples of isotopes are Protium, Deuterium, and Tritium, which are all Hydrogen atoms. Instead of the zero neutrons Hydrogen has in its Protium form, Deuterium and Tritium have two and three neutrons respectively. This change in neutron number and…