10 Calcium Facts

Cool Facts about the Element Calcium

Calcium is a metal. It readily oxidizes in air. Because it makes up such a large part of the skeleton, about one-third of the mass of human body comes from calcium, after water has been removed. Jurii / Wikimedia Commons / CC BY 3.0

Calcium is one of the elements you need in order to live, so it's worth knowing a little bit about it. Here are some quick facts about the element calcium. You can find more calcium facts on the calcium facts page.

  1. Calcium is element atomic number 20 on the periodic table, which means each atom of calcium has 20 protons. It has the periodic table symbol Ca and an atomic weight of 40.078. Calcium isn't found free in nature, but it can be purified into a soft silvery-white alkaline earth metal. Because the alkaline earth metals are reactive, pure calcium typically appears dull white or gray from the oxidation layer that quickly forms on the metal when it's exposed to air or water. The pure metal can be cut using a steel knife.


  1. Calcium is the 5th most abundant element in the Earth's crust, present at a level of about 3% in the oceans and soil. It is present at about 70 parts per million by weight in the solar system. Natural calcium is a mixture of six isotopes, with the most abundant (97%) being calcium-40.


  2. The element is essential for animal and plant nutrition. Calcium participates in many biochemical reactions, including building skeletal systems, cell signaling, and moderating muscle action. It is the most abundant metal in the human body, found mainly in bones and teeth. If you could extract all of the calcium from the average adult person, you'd have about 2 pounds (1 kilogram) of the metal. Calcium in the form of calcium carbonate is used by snails and shellfish to construct shells.


  3. Vitamin D is essential for calcium absorption by the human body. Vitamin D is converted to a hormone which causes intestinal proteins responsible for calcium absorption to be produced.


  1. While calcium and its compounds are not considered to be toxic, ingesting too many calcium carbonate dietary supplements or antacids can cause milk-alkali syndrome, which is associated with hypercalcemia sometimes leading to fatal renal failure. Excessive consumption would be on the order of 10 g calcium carbonate/day, though symptoms have been reported upon ingesting as little as 2.5 g calcium carbonate daily.


  1. Calcium is used for making cement, making cheese, removing nonmetallic impurities from alloys, and as a reduction agent in the preparation of other metals. The Romans used to heat limestone, which is calcium carbonate, to make calcium oxide. The calcium oxide was mixed with water to make cement, which was mixed with stones to build aqueducts, amphitheaters, and other structures that survive to the present day.


  2. Pure calcium metal reacts vigorously and sometimes violently with water and acids.


  3. The element name "calcium" comes from the Latin word "calcis" or "calx" meaning "lime". In addition to occurrence in lime (calcium carbonate), calcium is found in the minerals gypsum (calcium sulfate) and fluorite (calcium fluoride).


  4. Calcium has been known since the 1st century, when the ancient Romans were known to make lime from calcium oxide.


  5. Though calcium has been known for thousands of years, it was not purifed as an element until 1808 by Sir Humphrey Davy (England).
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Helmenstine, Anne Marie, Ph.D. "10 Calcium Facts." ThoughtCo, Apr. 13, 2017, thoughtco.com/calcium-element-facts-606472. Helmenstine, Anne Marie, Ph.D. (2017, April 13). 10 Calcium Facts. Retrieved from https://www.thoughtco.com/calcium-element-facts-606472 Helmenstine, Anne Marie, Ph.D. "10 Calcium Facts." ThoughtCo. https://www.thoughtco.com/calcium-element-facts-606472 (accessed March 19, 2018).