Potassium, K Ar

Potassium (K, [Ar. v1), name from the English word potash (pot ashes), symbol from the Latin word kalium (alkali). Identified and isolated (1807) by Sir Humphry Davy. Silvery white, soft metal. 

By using K/Ar isotope ratios, potassium-containing rocks can be dated to their first formation, even through millions of years. 

Determine the age of the Zag meteorite, using potassium-argon (K-Ar) radiochemical dating. 

Harrison T. M. and McDougall I. (1982). The thermal significance of potassium feldspar K-Ar ages inferred from " °Ar/ Ar age spectrum results. Geochim. Cosmochim. Acta, 46 1811-1820. 

A popular method used to date rocks is the potassium-argon method. Potassium is abundant in rocks such as feldspars, hornblendes, and micas. The K-Ar method has been used to date the Earth and its geologic formations. It has also been applied to determine magnetic reversals that have taken place throughout the Earth s history. Another method used in geologic dating is the rubidium-strontium, Rb-Sr, method. Some of the oldest rocks on Earth have been dated with this method, providing evidence that the Earth is approximately 5 billion years old. The method has also been used to date moon rocks and meteorites. 

In conventional K- Ar dating, the abundance of potassium is measured on one aliquot of the sample and the argon abundance and isotopic composition are measured on another. The... 

Shown below are the Lewis electron dot structures for five elements sulfur (S), chlorine (Cl), argon (Ar), potassium (K), and calcium (Ca). Answer the questions below about these structures. 

Radioactive elements in rocks (see Section 2.8), most importantly potassium (K) and heavy elements such as radium (Ra), uranium (U) and thorium (Th), can release gases. Argon (Ar) arises from potassium decay and radon (Rn, a radioactive gas that has a half-life of 3.8 days) from radium decay. The uranium-thorium decay series results in the production of a particles, which are helium nuclei. Once these nuclei capture electrons, helium has effectively been added to the atmosphere. 

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