Calcium (Ca) is a vital element in life and health on Earth. A silvery white metal, calcium is a strong builder, from bone structure to materials used in construction. Calcium is ubiquitous and may be taken for granted, but what is this amazing element all about?
The fifth most abundant element in the universe, calcium is one of the most prevalent metals on Earth. Over 85% of the Earth's crust contains calcium in different mineral forms. Calcium is crucial for scientific fields such as chemistry, biology, and medicine.
In 1808 England, Sir Humphry Davy first isolates calcium by electrolyzing a blend of lime and mercuric oxide. When it comes into contact with the air, calcium quickly develops a grey-white oxide and nitride layer.
Calcium belongs to the alkaline earth metals group in the periodic table and is known for its reactivity, especially with water and acids. Metallic calcium is found in a solid state at room temperature. The name derives from Latin calx "lime", obtained by heating limestone.
Properties of Calcium
Atomic Number: 20
Atomic Weight: Approximately 40.08 g/mol
Density: 1.54 g/cm³
Melting Point: 842 °C (1,548 °F)
Boiling Point: 1,484 °C (2,703 °F)
Calcium is highly reactive and readily forms compounds with other elements. In its pure form, it is soft enough to be cut with a knife. It tarnishes in moisture and air. Calcium can react vigorously with water when heated and is useful in chemical reactions.
Calcium is abundant in the Earth's crust, primarily in the form of rocks and minerals. The most common sources include limestone (calcium carbonate), gypsum (calcium sulfate), and fluorite (calcium fluoride). Calcium is not typically found in elemental form due to its reactivity.
Limestone, primarily calcium carbonate (CaCO3), is vital in environmental processes, including carbon cycling. It absorbs about 25% of carbon dioxide emitted by human activities.
In nature, calcium is constantly recycled. Plants absorb calcium from the soil, integrating it into their structure. When animals consume these plants calcium is released in the body to build strong bones, teeth and shells.
Functions of Calcium in Nature
Biological Functions: In living organisms, calcium is essential for transmitting electrical impulses between nerve cells. It's important in muscle contraction, blood clotting, and the formation of bones and teeth.
Ecosystem: Calcium contributes to the structure of shells in marine organisms, the stability of coral reefs, and neutralization of soil acidity, which affects plant growth. For plants, calcium stabilizes cell walls, providing structural integrity.
Bacteria Sporosarcina pasteurii are calcium processers. Common in soil, the bacteria convert nutrients and calcium into calcium carbonate or calcite, basically limestone. This bacterium, S. pasteurii, deposits limestone as a binder (or glue), in coral reefs and to bind and stabilize soil.
Compounds and Reactions with Other Elements
Calcium forms numerous compounds. Some of the most notable include:
Calcium Carbonate (CaCO3): Found in chalk, limestone, and marble, widely used as a dietary supplement and antacid, and in construction materials. About 1.8 billion tons of calcium carbonate are used annually in construction alone.
Calcium Sulfate (CaSO4): Commonly known as gypsum, it has applications in plaster and drywall.
Calcium Phosphate (Ca3(PO4)2): Crucial for bone and tooth formation in organisms, it is also used in fertilizers, contributing over 80% of phosphorus content in agricultural soil.
Calcium's reactivity allows it to create strong ionic bonds with non-metals.
How an Eggshell is Formed
The creation of an eggshell is a fascinating biochemical process. The primary component of eggshells is calcium carbonate (CaCO3), created within a hen's reproductive system.
Calcium Intake
During egg production, the hen absorbs calcium from her diet. Calcium ions are drawn from her bloodstream and transported to the shell gland. There, they combine with carbonate ions to form CaCO3. This process occurs over about 20 hours.
Formation
As the egg forms in the hen's reproductive tract, calcium carbonate is deposited in layers around the developing egg to form the protective shell.
Strength
The eggshell structure allows it to be strong yet fragile, providing the necessary protection for the developing embryo while allowing for gas exchange. Notably, hens with diets rich in calcium produce eggshells with about a third more strength.
Health Uses of Calcium
Calcium salts, especially calcium acetate, may be taken as supplements. Calcium is crucial for maintaining healthy bodily functions:
Bone Health:
Calcium is essential for building and maintaining strong bones and teeth. It helps prevent osteoporosis, a condition where bones become weak and brittle.
Nerve Function
Calcium ions are important in neurotransmission, affecting brain function and muscle movement.
Cardiovascular Health:
Proper calcium levels are important for healthy heart rhythm and blood pressure regulation.
Prevention of Osteoporosis
As people age, bone density declines. Sufficient calcium intake, particularly when paired with vitamin D, can reduce the risk of osteoporosis. An estimated 200 million individuals are afflicted with osteoporosis worldwide.
Recent global data from the International Osteoporosis Foundation reveals 1 of every 3 women age 50 and above, as well as 1 out of every 5 men, will endure osteoporotic fractures.
Hormonal Secretion: Calcium helps release hormones and enzymes to manage bodily functions.
Other Uses of Calcium
Beyond health, calcium has diverse industrial applications:
Construction
Calcium compounds like cement are fundamental in construction projects. Calcium carbonate and calcium sulfate are foundational in building materials. About 15 billion pounds of calcium carbonate are used in cement production every year in the US.
Food Industry: Calcium is used as a food additive (E170) for acidity regulation and as a fortifying agent in products such as dairy, and plant-based alternatives.
Metal Production: Calcium is a reducing agent in metallurgical processes, effectively extracting metals from their ores.
Water Treatment
Calcium is used in water treatment processes, helping remove impurities and maintain proper pH levels essential for safe drinking water.
Agriculture
Calcium is essential for soil health and plant growth, often included in fertilizers to improve soil quality and enhance crop yield.
Facts About Calcium
Dietary Source
Dairy products, leafy greens, nuts, legumes and fish are excellent sources of calcium for human diets. Calcium is the most abundant mineral in the human body, with 99% in bones and teeth.
Daily Requirement
The recommended daily calcium intake ranges from 700 mg to 1,300 mg for adults, depending on age and gender, and pregnancy condition.
Agriculture
Calcium is vital for plant growth, influencing cell wall structure and nutrient uptake.
Mythology
Calcium is a silvery metal. In ancient Egypt, the gods have bones of silver.
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