Calcium Calcium Calcium is a chemical element with symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The
Calcium lactate Calcium lactate Calcium lactate is a white crystalline salt with formula , consisting of two lactate anions (CHOH) for each calcium cation . It forms several hydrates, the most common being the pentahydrate ·5. Calcium lactate is used in medicine, mainly to treat calcium deficiencies; and as a food additive with E number of E327. Some cheese crystals consist of calcium lactate. The lactate ion is chiral, with two enantiomers, D (−,"R") and L (+,"S"). The L isomer is the one normally synthesized and metabolized by living organisms, but some bacteria can produce the D form or convert the L