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.

Fast Facts: Calcium

  • Element Name: Calcium
  • Element Symbol: Ca
  • Atomic Number: 20
  • Standard Atomic Weight: 40.078
  • Discovered By: Sir Humphry Davy
  • Classification: Alkaline Earth Metal
  • State of Matter: Solid Metal
  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.
  2. Calcium is the 5th most abundant element in the Earth's crust, present at a level of about 3 percent in the oceans and soil. The only metals more abundant in the crust are iron and aluminum. Calcium is also abundant on the Moon. 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 percent) being calcium-40.
  3. 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.
  4. Dairy products and grains are the primary sources of dietary calcium, accounting or about three-quarters of dietary intake. Other sources of calcium include protein-rich foods, vegetables, and fruits.
  5. 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.
  6. Calcium supplementation is controversial. 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. Excessive calcium consumption has been linked to kidney stone formation and artery calcification.
  7. 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.
  8. Pure calcium metal reacts vigorously and sometimes violently with water and acids. The reaction is exothermic. Touching calcium metal can cause irritation or even chemical burns. Swallowing calcium metal can be fatal.
  9. 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).
  10. Calcium has been known since the first century CE, when the ancient Romans were known to make lime from calcium oxide. Natural calcium compounds are readily available in the form of calcium carbonate deposits, limestone, chalk, marble, dolomite, gypsum, fluorite, and apatite.
  11. Though calcium has been known for thousands of years, it was not purified as an element until 1808 by Sir Humphry Davy of England. Thus, Davy is considered to be the discoverer of calcium.


  • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 112.
  • Parish, R. V. (1977). The Metallic Elements. London: Longman. p. 34.
  • Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110.​
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Helmenstine, Anne Marie, Ph.D. "10 Calcium Facts." ThoughtCo, Oct. 29, 2020, thoughtco.com/calcium-element-facts-606472. Helmenstine, Anne Marie, Ph.D. (2020, October 29). 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 30, 2023).