Cesium (Cs), also spelled caesium, chemical element of Group 1 (also called Group Ia) of the periodic table, the alkali metal group, and the first element to be discovered spectroscopically (1860), by German scientists Robert Bunsen and Gustav Kirchhoff, who named it for the unique blue lines of its spectrum (Latin caesius, “sky-blue”). Continue reading from Encyclopedia Britannica
Cesium was the first element to be discovered with a spectroscope. It was discovered in 1860 by German chemists Robert Bunsen and Gustav Kirchhoff when they were analyzing the spectrum of mineral water, according to WebElements.
The first practical applications of cesium were realized in the 1920s, according to the USGS. Cesium was used in vacuum tubes to remove traces of remaining oxygen due to its ready nature to bond with it, and as a coating on heated cathodes to increase the electric current. In later decades, more uses for cesium arose, including photoelectric cells, spectrometers and catalysts for organic reactions. The high cost of cesium and the growing popularity of similar and cheaper technologies using other alkali metals reduced the use of cesium to a handful of applications. Continue reading from Live Science
Samples of cesium are kept in sealed containers, under an inert liquid or gas or in a vacuum. Otherwise, the element would react with air or water. The reaction with water is much more violent and energetic than the reaction between water and other alkali metals (e.g., sodium or lithium). Cesium is the most alkaline of the elements and reacts explosively with water to produce cesium hydroxide (CsOH), a strong base that can eat through glass. Cesium spontaneously ignites in air.
Although francium is predicted to be more reactive than cesium, based on its location on the periodic table, so little of the element has been produced no one knows for sure. For all practical purposes, cesium is the most reactive metal known to man. According to the Allen scale of electronegativity, cesium is the most electronegative element. Francium is the most electronegative element according to the Pauling scale.
Cesium is used in atomic clocks, photoelectric cells, as a catalyst to hydrogenate organic compounds, and as a 'getter' in vacuum tubes. The isotope Cs-137 is used in cancer treatments, to irradiate foods, and as a tracer for drilling fluids in the petroleum industry. Nonradioactive cesium and its compounds are used for infrared flares, to make specialty glasses, and in beer brewing. Continue reading from ThoughtCo
