'''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]]s 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 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]]s 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 explodes on contact with water. |