'''Cesium''' is an element<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> in the [[alkali metal]] 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 and almost explodes on contact with water. | '''Cesium''' is an element<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> in the [[alkali metal]] 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 and almost explodes on contact with water. |