Caesium

__Caesium__ Caesium is a chemical element with the symbol Cs and atomic number 55. Is it 1 of 5 elemental metals that is a liquid at room temperature.

Caesium was discovered by two German chemists in 1860. Robert Bunsen and Gustav Kirchhoff discovered caesium through flame spectroscopy.

Since the 1990s, the largest application of the element has been as caesium formate for drilling fluids. It has a range of applications in the production of electricity, in electronics, and in chemistry. The radioactive isotope caesium-137 has a half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology. Although the element is only mildly toxic, it is a hazardous material as a metal and its radioisotopes present a high health risk in case of radiation leaks. Its physical properties are very soft, silvery-white, and it develops a silvery-gold hue. Its melting point is 28.4 degrees C which makes it one of the few elements which are liquid near room temperature. Mercury is the only elemental metal with a known melting point lower than caesium. Caesium also has a low boiling point of 641 degrees C. It burns with a blue color. Caesium forms allows with other alkali metals as well as with gold, amalgams, and mercury. When it reaches a room temperature of 650 degrees C, it alloys with cobalt, iron, molybdenum, nickel, platinum, tantalum, or tungsten.This metal is highly reactive and very pyrophoric. It can ignite spontaneously in air and explosively in water even at low temperatures. Therefore, it is classified as a hazardous material.

**The appearance of Caesium in its natural state is a soft, gold-coloured metal that is quickly attacked by air and reacts explosively in water. It is used in industry as a catalyst promoter, to make special glass, and in radiation monitoring equipment. The ‘caesium clock’ (atomic clock) is the standard measure of time: the electron resonance frequency of the caesium atom is 9,192,631,770 cycles per second. It is non-toxic and does not have a biological use.**
 * Uses of Caesium**
 * used as a catalyst in the hydrogenation of a few organic compounds
 * the metal can be used in ion propulsion systems. Although not usable in the earth's atmosphere, 1 kg of caesium in outer space could propel a vehicle 140 times as far as the burning of the same amount of any known liquid or solid. It is more efficient than rubidium.
 * used in atomic clocks
 * because of its high oxygen affinity, the metal is used as a "getter" in electron tubes
 * used in photoelectric cells and vacuum tubes
 * IR lamps