Large pollucite deposits have also been discovered in Zimbabwe, as well as in lithium-bearing pegmatites in Bernic Lake in Manitoba, Canada. The Tanco Mine in Manitoba, Canada is the leading and most abundant source of caesium in the world, with an estimated 350,000 metric tons of pollucite ore, representing over two-thirds of the global pollucite reserves. Pollucite is the only economically significant source mineral for caesium. These include several unusual types of beryl, avogadrite, and rhodizite. Only a few minerals contain considerable amounts of caesium. Despite being chemically similar to rubidium, it is 30 times less abundant than rubidium. It is more abundant than a few well-known metals like tungsten, antimony, and cadmium. OccurrenceĬaesium is found in small amounts, around 3 parts per million, in the Earth’s crust in the minerals pollucite, rhodizite, and lepidolite. Prior to this time, the element had no significant practical applications. Before the 1920s, it was primarily used in vacuum tubes as a “getter” to remove trace amounts of oxygen and other gasses that became trapped in the tube when it was sealed. It was not until later, when German chemist Carl Setterberg at the University of Bonn electrolyzed caesium cyanide CsCN, that pure caesium metal was successfully isolated.Ĭaesium has traditionally been used mostly in research and development. They attempted to create elemental caesium through the electrolysis of molten caesium chloride, but instead obtained a blue, homogeneous substance. Kirchhoff were the first to discover the element caesium through spectroscopic means, using the spectroscope they had just invented the year before. Gustav Kirchhoff (left) and Robert Bunsen | source: Science History Institute It is one of the elements with the most isotopes, with 40 known isotopes ranging from Caesium-112 to Caesium-151. With a Pauling scale value of 0.79, it is the least electronegative element. Due to its reactive nature, caesium is considered a hazardous material and must be stored and transported separately for safety reasons. This highly reactive silvery metal melts just above room temperature at 28.5 ℃ (83.3 ℉). It is a relatively rare element, with a total abundance in the Earth’s crust of about 3 parts per million.Ĭaesium reacts spontaneously in the air, which makes it hard to handle. In 1860, German chemist Robert Bunsen and physicist Gustav Kirchhoff discovered caesium using the newly invented method of flame spectroscopy. It is a soft, silvery-gold alkali metal whose name comes from the Latin word “caesius” (which means sky blue). Caesium (Cs), also spelled as cesium in American English, is a chemical element of the periodic table, located in group 1 and period 6, and has the atomic number 55.
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