Calcium

Calcium is a chemical element with the symbol Ca and atomic number 20. It belongs to the group of alkaline earth metals, a class of elements that react readily with water and air. In its standard state, it is a silvery-white solid metal.

Calcium does not occur naturally in its pure elemental form, as it combines rapidly with other elements. It is commonly found in compounds such as calcium carbonate (limestone and marble), gypsum (calcium sulphate), and calcium phosphate, which makes up the largest portion of bone mineral.

Chemical Properties

Calcium has two electrons in its outermost shell, so it readily forms ions marked as Ca²⁺. When exposed to water, it releases hydrogen and calcium hydroxide. In air, its surface forms an oxide layer that resists further oxidation.

Role in Living Organisms

Calcium is the most abundant mineral in the human body. The majority is found in bones and teeth, where it forms crystalline phosphate structures. A small fraction in the blood and cells takes part in muscle contraction, transmission of nerve signals, and blood clotting. Blood calcium levels are regulated by hormones, including parathyroid hormone and vitamin D.

Industrial Uses

Calcium and its compounds are used in construction (cement and limestone), metal production (to remove oxygen and impurities), and agriculture to improve soil acidity. It is also used in pharmaceuticals and food fortification to enhance mineral content.