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Cesium is an element<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref>in the Alkali metals class of the periodic table.  It is so chemically active that it is never found free (in elemental form) in nature, and catches fire on mere exposure to air.

Cesium is an element<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref>in the Alkali metals class of the periodic table.  It is so chemically active that it is never found free (in elemental form) in nature, and catches fire on mere exposure to air.

It was discovered by Robert Bunsen and Gustav Kirchoff, using their newly invented spectroscope, and was the first element discovered spectroscopically.  It (along with [[rubidium]]) was identified by a previously unseen blue spectral line in the analysis of mineral water from a German spa.  The name comes from that color.

It was discovered by Robert Bunsen and Gustav Kirchoff, using their newly invented spectroscope, and was the first element to be discovered spectroscopically.  It (along with [[rubidium]]) was identified by a previously unseen blue spectral line in the analysis of mineral water from a German spa.  The name comes from that color.

==References==

==References==