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 chloride quickly treat calcium channel blocker toxicity, from the side effects of drugs such as diltiazem. While intravenous calcium has been used to treat cardiac arrest, its general use is not recommended. Cases of cardiac arrest in which it is still recommended include high blood potassium, low blood calcium such as may occur following blood transfusions, and calcium channel blocker overdose. There is the potential that general use could worsen outcomes. If calcium is used, calcium chloride is generally the recommended form. Aqueous calcium chloride is used in genetic transformation of cells by increasing the cell membrane permeability, inducing competence for