Rubidium Standards

There are 48 neutrons in a standard Rubidium…?

but the isotope has 50 neutrons…why?

This question is a repeat, I answered it last night, same answer – different neutrons are what make isotopes.

Before the advent of absolute dating methods in the twentieth century, almost all appointments was relative. The main relative dating method is stratigraphy, which is the study of rock layers or embedded objects on layers. This method is based on an assumption (almost always true) that the deeper layers of rock were deposited before in the history of the Earth, and therefore is older than the most superficial layers. Successive layers of rock represent successive time intervals. Since that some species of animals on Earth at certain times in history, fossils or animal remains embedded in the layers of rock also help scientists determine the age of the layers. Similarly, they became fossilized pollen grains released by seed plants in the rock layers. If a certain type of pollen found at an archaeological site, scientists can see when the plant that produced the pollen lived to determine the relative age of the site.

Absolute dating methods are performed in a laboratory. Absolute dates must agree with the dates of other related methods in order to be valid. The most widely used and accepted form of absolute dating is radioactive decay dating. Radioactive decay is the process in which a radioactive form of an element becomes a radioactive product at a regular pace. The core of each radioactive element (such as radium and uranium) spontaneously decays with time, becoming in the nucleus of an atom of a different element. In the process of decay, the atom gives off radiation. Hence the term radioactive decay has been coined. Each element decays at its own pace, unaffected by external physical conditions. By measuring the amount of atoms of original and transformed into an object, scientists determine the age of the object.

The age of the remains of plants, animals and other organic materials can be determined by measuring the amount of carbon-14 in that material. Carbon-14, a radioactive form of the element carbon is created in the atmosphere by cosmic rays. When carbon-14 falls Earth is absorbed by plants. These plants are eaten by herbivores, which in turn are eaten by carnivores (even larger) animals. Finally, entire ecosystem of the planet, including humans, is filled with a carbon-14 concentration. While a body is alive, replenished the supply of carbon-14. When the organism dies, it stops the supply, and carbon-14 in the body begins to decay spontaneously nitrogen-14. The time it takes for half of the carbon-14 to Caries (a period called a half-life) is 5730 years. By measuring the amount of carbon-14 remaining, scientists can determine the exact date of death of the organism. The range of conventional radiocarbon dating is 30,000 to 40,000 years. With the sensitive instrumentation, this range can be extended to 70,000 years. Besides the technical radiocarbon dating, scientists have developed other methods of dating based on the transformation of one element into another. These include the uranium-thorium the potassium-argon method, the method and the rubidium-strontium method.

Thermoluminescence is useful for determining the age of pottery. When a piece of pottery is heated in a laboratory at temperatures over 500 ° C (930 ° F), the electrons in quartz and other minerals in the clay pottery emit light. The oldest is the pottery is brighter than the light being emitted. Use of thermoluminescence, ceramics as old as 100,000 years can be dated with precision. Known as dendrochronology, tree ring dating is based on the fact that trees produce one growth ring each year. Narrow growth rings in cold or dry years, and across the rings grow in hot or humid years. The rings form a distinctive pattern, which is the same for all members of a particular species and geographical area. Thus, the growth pattern of a known age of a tree can be used as a standard to determine the age of similar trees. The ages of the buildings and archaeological sites can also be determined by examining patterns of tree rings used in its construction. Dendrochronology has a range of 1 to 10,000 years or more.

About the Author:

Dr.Badruddin Khan teaches Chemistry in the University of Kashmir, Srinagar, India.

Article Source: ArticlesBase.com – What are Dating Techniques?