Potassium radioactive isotope

Seventeen isotopes of potassium are known. Ordinary potassium is composed of three isotopes, one of which is 40oK (0.0118%), a radioactive isotope with a half-life of 1.28 x IO9 years. 

The constant half-life of a nuclide is used to determine the ages of archaeological artifacts. In isotopic dating, we measure the activity of the radioactive isotopes that they contain. Isotopes used for dating objects include uranium-238, potassium-40, and tritium. However, the most important example is radiocarbon dating, which uses the decay of carbon-14, for which the half-life is 5730 a. 

Among those elements are a number that are entirely radioactive or have isotopes that are radioactive. The element potassium, a critical electrolyte in the blood, includes the radioactive isotope K-40. 

We observe it in the decay of some radioactive isotopes, such as potassium-40 ... 

They produce distinctive colored flames when burned lithium = crimson sodium = yellow potassium = violet rubidium = purple cesium = blue and the color of francium s flame is not known. Many of francium s characteristics have not been determined owing to the fact that it is rare and all of its many radioactive isotopes have short half-lives. 

A particular hazard, which has been with humans since the beginning of time, is the radioactive isotope potassium-40 (K-40). Less than 1% of all potassium atoms on Earth are in the form of this radioactive isotope. It has a half-life of 1.25 billion years. Its decay process... 

There are three naturally occurring isotopes, 39K through 41K, of which 40K is radioactive with a half-life of 1.3 109 years. Tn ordinary potassium, this isotope represents only 0.0119% of the content. There are four other known isotopes, all radioactive. 33 K and 42K through 44K, all with relatively short half-lives measured in minutes and hours. In terms of abundance, potassium ranks seventh among the elements occurring in the earth s crust. In terms of content in seawater, the element ranks eighth, with an estimated 1,800,000 tons of potassium per cubic mile (388,000 metric tons per cubic kilometer) of seawater, First ionization potential 4,339 eV ... 

An isotope of carbon called carbon-14 offers a glimpse of how humans may have lived thousands of years ago. The radioactive isotope decays steadily to become nitrogen-14 in a way that is similar to the decay of potassium into argon, making it useful for dating plants, bones, and other organic materials that once contained... 

Potassium has two stable isotopes (39K and 41K) and one naturally occurring radioactive isotope (4°K). Thelast, via its decay, accounts for the high abundance of 40 Ar in the Earth s atmosphere. It also provides a valuable means of dating ancient rocks. Potassium nucleosynthesis derives almost entirely from a single main-line source, the fusion of oxygen in massive stars that will become Type II supernovae. 

We know that nuclear weapons are capable of mass destruction, yet radiation therapy, shown in Figure 4.18, is a proven cancer fighter. Smoke detectors, required by law in all homes, rely on the radioactive decay of americium-241. The human body itself is radioactive, due to the presence of radioactive isotopes including carbon-14, phosphorus-32, and potassium-40. Most people view radioactivity and nuclear reactions with a mixture of fascination, awe, and fear. Since radioactivity is all around us, it is important to understand what it is, how it arises, and how we can deal with it safely. 

Major concern about rapidly increasing levels of radioactive fallout in the environment and in foods developed as a result of the extensive testing of nuclear weapons by the United States and the Soviet Union in the 1950s. Nuclear fission generates more than 200 radioisotopes of some 60 different elements. Many of these radioisotopes are harmful to humans because they may be incorporated into body tissues. Several of these radioactive isotopes are absorbed efficiently by the organism because they are related chemically to important nutrients for example, strontium-90 is related to calcium and cesium-137 to potassium. These radioactive elements are produced by the following nuclear reactions, in which the half-life is given in parentheses ... 

Potassium and sodium were first isolated within a few days of each other in 1807 by Humphry Davy as products of the electrolysis of molten KOH and NaOH. In 1817, J. A. Arfvedson, a young chemist working with J. J. Berzelius, recognized similarities between the solubilities of compounds of lithium and those of sodium and potassium. The following year, Davy also became the first to isolate lithium, this time by electrolysis of molten Li20. Cesium and rubidium were discovered with the help of the spectroscope in 1860 and 1861, respectively they were named after the colors of the most prominent emission lines (Latin, caesius, sky blue, rubidus, deep red). Francium was not identified until 1939 as a short-lived radioactive isotope from the nuclear decay of actinium. 

The radiochemical procedure for the determination of Cs in aqueous samples is based on the batch extraction of caesium onto a microcrystalline cation exchanger, ammonium molybdophosphate (AMP), and subsequent purification from potassium and rubidium activities by ion-exchange separation using a strongly acidic cation exchange resin (BIO-REX-40). Natural K and Rb have radioactive isotopes that interfere with the beta counting of Cs. The purification of caesium is also necessary to determine the chemical recovery. 

No radioactive isotopes of argon have any practical application. One non-radioactive isotope is used, however, to find the age of very old rocks. This method of dating rocks is described in the potassium entry. 

There are three naturally occurring isotopes of potassium potassium-39, potassium-40, and potassium-41. Potassium-40 is radioactive. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element s name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. 

Eighteen artificial radioactive isotopes of potassium with measured half lives are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Artificially radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive. 

As you may know, some common everyday substances are radioactive. In this lab you will investigate the three naturally occurring potassium isotopes found in a common store-bought salt substitute. Two of potassium s isotopes, potassium-39 (93.1%) and potassium-41 (6.89%) are stable. However, potassium-40 (0.01%) decays by beta emission to form stable calcium-40. You will first measure the background radiation level, and then use that information to determine the radiation due to the beta decay of potassium-40. You will also measure radiation at various locations around your school. 

CAS 7440-09-7. K. Metallic element of atomic number 19, group IA of the periodic table, an alkali metal, aw 39.098, valence of 1. Potassium-40 is a naturally occurring radioactive isotope. There are also two stable isotopes. The synthetic isotope, po-tassium-42, is used in tracer studies, primarily in medicine. An essential element in plant growth and in animal and human nutrition occurs in all soils. 

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