Calcium::calcium    Author::journal    Title::first    Volume::pages    Issue::mineral    Water::dietary

{{#invoke:Hatnote|hatnote}} {{#invoke:Protection banner|main}}{{#invoke:Pp-move-indef|main}} {{#invoke:Infobox|infobox}}

Calcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft gray alkaline earth metal, fifth-most-abundant element by mass in the Earth's crust. The ion Ca2+ is also the fifth-most-abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Free calcium metal is too reactive to occur in nature. Calcium is produced in the explosions at the end of the life of massive stars

Calcium is essential for living organisms, in particular in cell physiology, where movement of the calcium ion into and out of the cytoplasm functions as a signal for many cellular processes. As a major material used in mineralization of bone, teeth and shells, calcium is the most abundant metal by mass in many animals.

Calcium sections
Intro  Notable characteristics  Compounds  Isotopes  Geochemical cycling  History  Occurrence  Applications  Nutrition  Hazards and toxicity  See also  References  Further reading  External links  

PREVIOUS: IntroNEXT: Notable characteristics