Properties and Overview of Calcium

Overview:

Calcium (Ca) is a chemical element with the atomic number 20 and the symbol Ca on the periodic table. It is an essential element in the Earth's crust and is one of the most abundant metals, making up about 3.5% of the planet's crust. Calcium is also crucial for living organisms, playing a pivotal role in biological processes, particularly in the structure and function of bones and teeth in humans and other animals. The element was first isolated in 1808 by Sir Humphry Davy through the electrolysis of a mixture of lime (CaO) and mercuric oxide (HgO). Physically, calcium is a silvery-white metal that is relatively soft, meaning it can be easily cut with a knife. It has a melting point of approximately 840°C and a boiling point of 1,480°C, which are moderate for a metal. Calcium is lighter than many other metals, with a density of approximately 1.5 g/cm³. Despite being reactive, calcium forms a thin, protective oxide layer when exposed to air, which helps prevent further oxidation. However, it must still be handled carefully in pure form due to its reactivity with water and air. Calcium's relatively low density and reactivity make it a crucial material in various metallurgical and industrial processes.
Chemically, calcium is an alkaline earth metal belonging to group 2 of the periodic table. It has two valence electrons, which it readily loses to form a divalent cation (Ca²⁺). This makes calcium highly reactive, particularly with water and acids. In water, calcium forms calcium hydroxide (Ca(OH) ₂) and hydrogen gas, a reaction that releases heat. Calcium's reactivity also allows it to participate in the formation of a wide range of compounds. Calcium carbonate (CaCO₃) is perhaps the most well-known of these, forming the basis of limestone, marble, and chalk, and is widely used in construction and cement production. Calcium oxide (CaO), also known as lime or quicklime, is another essential compound used in the manufacture of steel and glass and as a chemical reagent. Calcium hydroxide, or slaked lime, is used in agriculture to neutralize acidic soils and water treatment processes. Calcium sulfate (CaSO₄) is used to produce plaster and drywall.
Safety considerations regarding calcium pertain mainly to its chemical reactivity, particularly in its pure form. Metallic calcium is highly reactive and can ignite in the presence of air or water, producing calcium hydroxide and hydrogen gas, which is flammable. Therefore, it must be handled with care, typically under an inert atmosphere such as argon or in an oil, to prevent accidental ignition. Calcium is vital for health in the human body, but an imbalance, either too much or too little, can lead to medical issues. Excessive intake can cause hypercalcemia, which may lead to kidney stones or impaired absorption of other essential minerals. Conversely, calcium deficiency can weaken bones, osteoporosis, and other health problems. Handling calcium compounds in industrial and laboratory settings generally requires standard safety precautions, such as wearing protective gear and ensuring proper ventilation to avoid inhaling dust or fumes, particularly from more reactive compounds like calcium carbide or calcium oxide.

Production:

The production of calcium metal involves the electrolysis of molten calcium chloride (CaCl₂). This process is carried out in a specially designed electrolytic cell where calcium ions are reduced at the cathode, producing pure calcium metal. The calcium chloride used in this process is typically derived from natural sources, such as limestone (calcium carbonate), or as a byproduct of other chemical processes. Another method of producing calcium is reducing lime with aluminium at high temperatures, though this method is less common. In addition to metallic calcium, calcium compounds like calcium carbonate, calcium oxide, and calcium hydroxide are produced on a large scale for various industrial applications.

Applications:

Calcium plays a crucial role in the biological systems of all living organisms. In humans, it is the most abundant mineral in the body, with about 99% stored in bones and teeth, providing structural strength. Calcium is also vital in other physiological processes, including muscle contraction, blood clotting, and the functioning of the nervous system. It acts as a secondary messenger in many cellular processes and is necessary to activate certain enzymes. Calcium ions are involved in the release of neurotransmitters in synaptic transmission and play a role in regulating the heartbeat. Dietary sources of calcium include dairy products, leafy green vegetables, nuts, and fish. Calcium supplements are commonly used to ensure adequate intake, particularly in populations at risk of deficiency, such as the elderly or those with dietary restrictions.
In industrial applications, calcium is used primarily in its compound forms. Calcium carbonate is one of the most versatile and widely used materials in products, from construction materials to dietary supplements. It is a critical ingredient in the production of cement and lime, which are fundamental to the construction industry. In agriculture, calcium compounds improve soil quality and pH balance. Calcium oxide is used in steel manufacturing as a flux to remove impurities during smelting. It is also used in the production of glass, where it improves durability and chemical resistance. Calcium chloride is used for de-icing roads, as a desiccant, and in the food industry as a firming agent. In the chemical industry, calcium compounds are reagents, catalysts, and intermediates in various reactions.

Summary:

Calcium is a highly reactive, essential element with many applications in industry, biology, and everyday life. Its chemical and physical properties make it invaluable in producing materials like cement and glass. At the same time, its biological importance cannot be overstated, particularly in maintaining bones and teeth' structural integrity and supporting various physiological functions. Despite its reactivity and the safety precautions required when handling it in pure form, calcium's benefits in both industrial and biological contexts are significant.

See a comprehensive list of atomic, electrical, mechanical, physical and thermal properties for calcium below: