![]() ![]() Some small differences arise from the fact that it has a higher atomic mass and is more electropositive than other (nonradioactive) alkali metals. As expected for an alkali metal, the only common oxidation state is +1. The chemistry of caesium is similar to that of other alkali metals, in particular rubidium, the element above caesium in the periodic table. In quantities of more than about 100 grams (3.5 oz), caesium is shipped in hermetically sealed, stainless steel containers. Caesium can be stored in vacuum-sealed borosilicate glass ampoules. This is because caesium explodes instantly upon contact with water, leaving little time for hydrogen to accumulate. However, a caesium-water explosion is often less powerful than a sodium-water explosion with a similar amount of sodium. It can be handled only under inert gas, such as argon. It is stored and shipped in dry, saturated hydrocarbons such as mineral oil. Because of this high reactivity, caesium metal is classified as a hazardous material. It reacts with solid water at temperatures as low as −116 ☌ (−177 ☏). It ignites spontaneously in air, and reacts explosively with water even at low temperatures, more so than the other alkali metals ( first group of the periodic table). Chemical propertiesĬaesium metal is highly reactive and very pyrophoric. A few amalgams have been studied: CsHgĢ is black with a purple metallic lustre, while CsHg is golden-coloured, also with a metallic lustre. It mixes with all the other alkali metals (except lithium) the alloy with a molar distribution of 41% caesium, 47% potassium, and 12% sodium has the lowest melting point of any known metal alloy, at −78 ☌ (−108 ☏). It forms well-defined intermetallic compounds with antimony, gallium, indium, and thorium, which are photosensitive. At temperatures below 650 ☌ (1,202 ☏), it does not alloy with cobalt, iron, molybdenum, nickel, platinum, tantalum, or tungsten. Its compounds burn with a blue or violet colour.Ĭaesium forms alloys with the other alkali metals, gold, and mercury ( amalgams). In addition, the metal has a rather low boiling point, 641 ☌ (1,186 ☏), the lowest of all metals other than mercury. Mercury is the only elemental metal with a known melting point lower than caesium. It has a melting point of 28.4 ☌ (83.1 ☏), making it one of the few elemental metals that are liquid near room temperature. It is a very ductile, pale metal, which darkens in the presence of trace amounts of oxygen. Although the element is only mildly toxic, the metal is a hazardous material and the radioisotopes would present a significant health and ecological hazard in the environment.Ĭaesium is the softest metallic element (it has a hardness of 0.2 Mohs). The radioactive isotope caesium-137 has a half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology. Since the 1990s, the largest application of the element has been as caesium formate for drilling fluids, but it has a range of applications in the production of electricity, in electronics, and in chemistry. Since then, caesium has been widely used in highly accurate atomic clocks. In 1967, acting on Einstein's proof that the speed of light is the most constant dimension in the universe, the International System of Units used two specific wave counts from an emission spectrum of caesium-133 to co-define the second and the metre. The first small-scale applications for caesium were as a " getter" in vacuum tubes and in photoelectric cells. The German chemist Robert Bunsen and physicist Gustav Kirchhoff discovered caesium in 1860 by the newly developed method of flame spectroscopy. Reacting fluorine with caesium first time on camera.Caesium in water slow motion periodic table of videos.Caesium is mined mostly from pollucite, while the radioisotopes, especially caesium-137, a fission product, are extracted from waste produced by nuclear reactors. It has only one stable isotope, caesium-133. It is the least electronegative element, with a value of 0.79 on the Pauling scale. Some argue that caesium is the most reactive element of all, even more reactive than fluorine, the most reactive nonmetal. The metal is extremely reactive and pyrophoric, reacting with water even at −116 ☌ (−177 ☏). ![]() ![]() Caesium is an alkali metal and has physical and chemical properties similar to those of rubidium and potassium. It is a soft, silvery- gold (or, according to some, silver/colorless) alkali metal with a melting point of 28.5 ☌ (83.3 ☏), which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium or cesium is a chemical element with symbol Cs and atomic number 55. ![]()
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