The radioactivity presents no appreciable hazard. Ordinary potassium is composed of three isotopes, one of which is 40°K (0.0118%), a radioactive isotope with a half-life of 1.28 x 10 9 years. Seventeen isotopes of potassium are known. Potassium and its salts impart a violet color to flames. It rapidly oxidizes in air and must be preserved in a mineral oil such as kerosene.Īs with other metals of the alkali group, it decomposes in water with the evolution of hydrogen. It is soft, easily cut with a knife, and is silvery in appearance immediately after a fresh surface is exposed. Except for lithium, it is the lightest known metal. It is one of the most reactive and electropositive of metals. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure. It is a silvery white metal that is soft enough to easily cut with a knife. Many potassium salts are of utmost importance, including the hydroxide, nitrate, carbonate, chloride, chlorate, bromide, iodide, cyanide, sulfate, chromate, and dichromate. Potassium is the chemical element with the symbol K (from Neo-Latin kalium) and atomic number 19. Potassium is an essential constituent for plant growth and is found in most soils.Īn alloy of sodium and potassium (NaK) is used as a heat-transfer medium. But the valency of elements, when combined with H or O first, increases from 1 to 4 and then it reduces to zero. While moving left to right across a period, the number of valence electrons of elements increases and varies between 1 to 8. Variation Of Oxidation State Along a Period. The greatest demand for potash has been in its use for fertilizers. Periodic Trends in the Oxidation States of Elements. Thermal methods also are commonly used to produce potassium (such as by reduction of potassium compounds with CaC 2, C, Si, or Na). Potassium is never found free in nature, but is obtained by electrolysis of the hydroxide, much in the same manner as prepared by Davy's first process. Potassium is also found in the ocean, but is present only in relatively small amounts, compared to sodium. Large deposits of potash, found at a depth of some 3000 ft in Saskatchewan, promise to be important in coming years. Potash is mined in Germany, New Mexico, California, Utah, and elsewhere. Most potassium minerals are insoluble and the metal is obtained from them only with great difficulty.Ĭertain minerals, however, such as sylvite, carnallite, langbeinite, and polyhalite are found in ancient lake and sea beds and form rather extensive deposits from which potassium and its salts can readily be obtained. The metal is the seventh most abundant and makes up about 2.4% by weight of the earth's crust. Discovered in 1807 by Davy, who obtained it from caustic potash (KOH) this was the first metal isolated by electrolysis. Consider the positions of barium (Ba), sulfur (S), silicon (Si), and calcium (Ca) on the periodic table. Electronegativities A partial periodic table. From the English word, potash - pot ashes Latin kalium, Arab qali, alkali. The periodic table below shows the electronegativity values of some elements.
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