6/7/2023 0 Comments Chromium melting point![]() A tracer is a radioactive isotope whose presence in a system can easily be detected. This isotope is used as a tracer in studies on blood. One radioactive isotope of chromium is used in medical research, chromium-51. These particles stick in the atoms and make them radioactive.Ĭhromium compounds' colors range from purple and black to green, orange, and yellow. Radioactive isotopes are produced when very small particles are fired at atoms. A radioactive isotope is one that breaks apart and gives off some form of radiation. Seven radioactive isotopes of chromium are known also. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number written to the right of the element's name is the mass number. Isotopes differ from each other according to their mass number. Isotopes are two or more forms of an element. There are four naturally occurring isotopes of chromium: chromium-50, chromium-52, chromium-53, and chromium-54. There are no chromite mines in the United States. Other important producers are Kazakhstan, Turkey, India, Finland, Albania, and Brazil. The leading producer of chromite ore is South Africa. Today, nearly all chromium is produced from chromite, or chrome iron ore (FeCr 2O 4). It ranks about number 20 among the chemical elements in terms of their abundance in the earth.Ĭhromium does not occur as a free element. The abundance of chromium in the Earth's crust is about 100 to 300 parts per million. Chromium oxideįorms a thin layer on the surface of the metal, protecting it from further corrosion (rusting). It combines with oxygen at room temperature to form chromium oxide (Cr 2O 3). It does not react with water, but reacts with most acids. Chemical propertiesĬhromium is a fairly active metal. One important property is that chromium can be polished to a high shine. The density is 7.1 grams per cubic centimeter. Physical propertiesĬhromium is a hard, steel-gray, shiny, metal that breaks easily. The colors range from purple and black to green, orange, and yellow. The name chromium was suggested by two French chemists, Antoine Francois de Fourcroy (1755-1809) and Ren é-Just Ha üy (1743-1822), because chromium forms so many different colored compounds. When the reaction was complete, he found tiny metallic needles of chromium metal: He heated charcoal (nearly pure carbon ) with a compound of chromium, chromium trioxide (Cr 2O 3). He reported "a new metal, possessing properties entirely unlike those of any other metal."Ī year later, Vauquelin was able to isolate a small sample of the metal itself. None of the elements then known could account for his results. ![]() He was convinced that the mineral contained a new element. In 1797, Vauquelin began his own studies of Siberian red lead. ![]() They guessed that it contained lead as well as arsenic, molybdenum, or some other metal. Scientists had only small amounts of the mineral to study. It was mined at only one location in Germany and miners found it difficult to remove. Studies of Siberian red lead were difficult, however. In some cases, it was found, as some said, "attached like little rubies to quartz." It had a form and a color not seen in other minerals. Scientists were puzzled about what elements this new mineral contained. The mineral was first described in 1766 by German mineralogist Johann Gottlob Lehmann (1719-67). This technique protects the base metal and gives the surface a bright, shiny appearance at a low cost.Ĭhromium was discovered in a mineral known as Siberian red lead. Chromium is also used to cover the surface of other metals. The mixture has different properties than the individual metals. An alloy is made by melting and mixing two or more metals. The name comes from the Greek word chroma, meaning "color," because chromium compounds are many different colors.Ībout three-quarters of chromium produced today is used in alloys, including stainless steel. They have a bright, shiny surface and high melting points.Ĭhromium was discovered in 1797 by French chemist Louis-Nicolas Vauquelin (1763-1829). These elements all have similar physical and chemical properties. Elements in Groups 3 through 12 are known as the transition metals. OverviewĬhromium is found in the center of the periodic table, a chart that shows how chemical elements are related to each other. Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.
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