calcium

calcium
Number	20
Category	Alkaline earth metal
Standard atomic weight	40.078
Electron configuration	[Ar] 4s2
Phase	Solid
Melting point	842 °C
Boiling point	1484 °C
Named after	Latin calx (lime)
Discoverer	Humphry Davy
Discovery date	1808

calcium. A chemical element with the symbol Ca and atomic number 20, it is an essential Alkaline earth metal that is abundant in the Earth's crust. It is a soft, silvery-white metal that reacts readily with Oxygen and Water. Its compounds, particularly Calcium carbonate and Calcium sulfate, are fundamental to numerous industrial, geological, and biological processes.

Chemical properties

In its pure form, it tarnishes quickly upon exposure to Air, forming a protective layer of Calcium oxide and Calcium nitride. It reacts vigorously with Water to produce Calcium hydroxide and Hydrogen gas, a reaction more moderate than that of Sodium or Potassium but more pronounced than Magnesium. Its position in group 2 gives it a stable +2 oxidation state, and its chemistry is dominated by ionic bonding, as seen in compounds like Calcium chloride and Calcium phosphate. The metal burns with a brilliant orange-red flame in air, forming primarily the oxide, and it also reacts directly with Halogens and Hydrogen to form corresponding salts.

Biological role

It is a critical signaling ion in all Eukaryotes, with its intracellular concentration tightly regulated by systems like the Sarcoplasmic reticulum. It is the key mineral component of Bones and teeth, primarily in the form of Hydroxyapatite. The ion is essential for processes such as Muscle contraction, Neurotransmitter release, Blood clotting (where it acts as a Cofactor for enzymes), and Cell division. Its homeostasis in the body is controlled by hormones including Parathyroid hormone, Calcitonin, and Calcitriol (the active form of Vitamin D). Deficiencies can lead to disorders like Osteoporosis and Rickets.

Occurrence and production

It is the fifth most abundant element in the Earth's crust, found extensively in sedimentary rocks like Limestone, Chalk, and Marble, which are chiefly composed of Calcium carbonate. Other major sources include Gypsum (calcium sulfate) and Fluorite (calcium fluoride). It is not found natively due to its high reactivity. The metal is produced industrially through the electrolysis of molten Calcium chloride, a method first employed by Humphry Davy. Major producers include China, Russia, and the United States.

Compounds

Its most prevalent compound is Calcium carbonate, found in Limestone and the shells of marine organisms like Foraminifera. Calcium oxide (quicklime), produced by heating carbonate, is a crucial industrial material used in Steelmaking and Cement production. Calcium sulfate exists as Gypsum and Anhydrite, used in Plaster of Paris and drywall. Calcium phosphate is the primary mineral in bones and a major component of Fertilizer. Other significant compounds include Calcium carbide, used historically in Acetylene lamps, and Calcium hypochlorite, a common disinfectant.

Applications

Metallic calcium is used as a reducing agent in the preparation of other metals, such as Thorium and Uranium. It serves as an alloying agent for Aluminium, Beryllium, Copper, and Lead alloys. Its compounds have vast applications: Calcium carbonate is a filler in Paper, Paint, and Plastic, and is the main ingredient in Antacids. Portland cement, a cornerstone of modern construction, relies on calcium silicates and aluminates. In agriculture, compounds like Calcium nitrate and lime are used to amend Soil pH and provide essential nutrients.

History

Lime (calcium oxide) has been used since antiquity in Mortar by civilizations like the Ancient Romans. The element was first isolated in 1808 by Humphry Davy in London through the electrolysis of a mixture of lime and Mercury oxide. Its name derives from the Latin word *calx*, meaning "lime." Throughout the 19th century, its role in Physiology began to be understood, notably through the work of Sidney Ringer on its necessity for Cardiac muscle contraction. The development of the Solvay process in the 1860s by Ernest Solvay revolutionized the production of sodium carbonate, using calcium compounds as key reagents.

Category:Chemical elements Category:Alkaline earth metals Category:Dietary minerals