Calcium

Calcium 40.078(4)   Ca 20 [Ar] 4s2 2,4,s [ ? ] Alkaline Earth Metal: Properties: Silvery-white, hard metal. Compounds: oxide (lime), carbonate, nitrate, sulfide, chloride, and others

Calcium is the chemical element with the symbol Ca and atomic number 20.

Calcium is essential for life, particularly in cell physiology, where movement of the calcium ion Ca²⁺ into and out of the cytoplasm functions as a signal for many cellular processes, including neuromuscular contractions. It is also a major material used in mineralization of bones, teeth and shells.