Calcium

Calcium is a chemical element with the symbol Ca and atomic number 20. It belongs to a group called the alkaline earth metals and is a reactive metal that changes when it touches air. Calcium is very common in the world around us—it is the fifth most abundant element in the Earth’s crust and the third most common metal, after iron and aluminium. We find it in rocks like limestone as a compound called calcium carbonate, and it is a part of many minerals such as gypsum, anhydrite, fluorite, and apatite.

People have used calcium compounds for thousands of years, even though they didn’t understand their chemistry until much later. The pure metal was first isolated in 1808 by Humphry Davy using a process called electrolysis. Today, calcium compounds are used in many ways, such as in foods and medicines for calcium supplementation, in making paper, cement, and soaps.

In our bodies, calcium is extremely important. It is the most abundant metal in the human body and plays many key roles. As calcium ions (Ca²⁺), it helps send messages between cells, allows nerves to release neurotransmitters, helps all kinds of muscle cells to contract, supports the work of many enzymes, and is needed for building strong bones.

Characteristics

Calcium is a soft, silvery metal that looks somewhat pale yellow. It shares many properties with other metals in its group, especially strontium and barium. Each calcium atom has 20 electrons, arranged in a specific pattern that makes it easy to lose two electrons in chemical reactions, forming a stable ion.

Calcium melts at 842°C and boils at 1494°C. It is softer than lead and can be cut with a knife, though it requires some effort. While not as good a conductor of electricity as copper or aluminium, it conducts better by mass due to its low density. Calcium reacts with water to produce calcium hydroxide and hydrogen gas, and it also reacts with oxygen and nitrogen in the air to form calcium oxide and calcium nitride. When burned, it produces these compounds as well. Calcium hydroxide is a strong base, and calcium carbonate and calcium sulfate are common minerals.

History

Calcium compounds have been used for thousands of years, even though people didn’t understand their chemical makeup until much later. For example, lime was used as a building material and for making statues as far back as 7000 BC. The ancient Romans used lime mortars made from heating limestone.

The name “calcium” comes from the Latin word for lime. In 1808, scientists first isolated calcium metal using a process called electrolysis. This was a big step in understanding this important element.

Occurrence and production

Calcium makes up about 3% of the Earth's crust, making it the fifth most common element overall and the third most common metal. It is also found in the lunar highlands. Much of the calcium on Earth is found in rocks and minerals such as limestone, dolomite, marble, chalk, and corals. Important calcium minerals include gypsum, anhydrite, fluorite, and apatite.

The biggest producers of calcium are China, Russia, and the United States. In Russia and China, calcium is made using a method involving electricity on melted calcium chloride. In the U.S. and Canada, calcium is produced by mixing lime with aluminium at very high temperatures.

Applications

Calcium is widely used in many important ways. One major use is in steelmaking, where it helps remove impurities like oxygen and sulfur, making the steel stronger and easier to work with. It is also used in special alloys for batteries and in drain cleaners, where it helps break down blockages.

Calcium compounds are used in many everyday products, such as food additives, medicines, and toothpaste. They help provide important nutrients and have various useful functions, like making toothpaste foam or helping medicines work better. Calcium supplements are also considered essential medicines around the world.

Food sources

See also: Calcium supplement

Many foods are rich in calcium, including dairy products like milk, yogurt, and cheese. You can also find calcium in fish such as sardines and salmon, as well as soy products, kale, and fortified breakfast cereals.

Health organizations have set limits on how much calcium people should consume each day to avoid health problems. These limits vary depending on age.

Biological and pathological role

Calcium is an important element needed by our bodies. The calcium ion helps keep our muscles, blood flow, and digestion working properly. It is also important for building strong bones and helps blood to clot. Our bodies carefully control calcium levels because it connects with many other substances, like proteins, to do its job.

Calcium can bind to different parts of proteins and other molecules, which helps it perform its many roles in the body. It also connects with fats in cell membranes, helping hold certain proteins in place. Our bodies get calcium from food and supplements, and hormones help control how much calcium is in our blood. Not having enough calcium can weaken bones, while too much can cause health problems.

Safety

Metallic calcium

Calcium is a reactive metal that can cause serious burns if it touches water or moisture on the skin. If swallowed, it can harm the mouth, throat, and stomach. While long-term exposure isn’t known to cause special problems, care should be taken around this metal to avoid injury.