What is Calcium? | Definition, Properties, Compounds, & Facts

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Calcium is the third element in the second column of the periodic table. It is classified as an alkaline earth metal. The calcium atom has 20 electrons and 20 protons has 2 valence electrons in the outermost shell. Calcium is an essential element for life on Earth and is the fifth most abundant element in the earth’s crust.

Highlights of Calcium:

Symbol Ca
Atomic Number 20
Atomic Weight 40.078
Classification Alkaline earth metal
Phase at Room Temperature Solid
Density 1.55 grams per cm cubed
Melting Point 842°C, 1548°F
Boiling Point 1484°C, 2703°F
Discovered by Sir Humphry Davy in 1808

Characteristics and Properties

Under normal conditions, calcium is a shiny, silvery metal. It is quite soft and is the lightest alkaline earth metal due to its low density. Although it has a shiny silver color when first cut, it quickly forms a grayish-white oxide layer on the surface when exposed to air.

When exposed to water, calcium reacts and produces hydrogen. When ignited, it produces a bright orange-red flame.

Where is Calcium found on Earth?

Calcium is rarely found in elemental form, but is readily found throughout the Earth, mainly in the form of rocks and minerals such as limestone (calcium carbonate), dolomite (calcium and magnesium carbonate) and gypsum (calcium sulfate). . It is the fifth most abundant element in the earth’s crust.

Calcium carbonate is one of the main components of many rocks and minerals, including limestone, marble, calcite, and chalk.

Calcium is also found in seawater and is the eighth most abundant element found in the ocean.

How is Calcium used today?

Calcium in its elemental form is of little industrial use, but its compounds with other elements are widely used.

An important compound is calcium oxide (CaO), also known as quicklime. Lime is used in a number of applications including metal production, pollution removal and water purification. It is also used to produce chemical supplements.

Calcium compounds, rocks and minerals such as limestone and marble are also used in construction. Gypsum is used to make plaster of Paris and drywall. Other uses include antacids, toothpastes, and fertilizers.

Calcium is also a very important element in plant and animal life. In the human body, calcium is part of a compound called hydroxyapatite, which helps to harden our bones and teeth. Calcium is the fifth most abundant element in the human body, accounting for about 1.4% of body mass.

How was it discovered?

The first scientist to discover and isolate the element calcium was British chemist Sir Humphry Davy in 1808.

Where did calcium get its name?

Sir Humphry Davy named calcium after the Latin word “calx”, which the Romans called lime.


Calcium has four stable isotopes, including 40Ca, 42Ca, 43Ca and 44Ca. The other two calcium isotopes (46Ca and 48Ca) have very long half-lives and are generally considered stable. About 97% of natural calcium is in the isotope form 40Ca.

Interesting Facts about Calcium

  • Most calcium salts dissolve readily in water.
  • Calcium is an important element in building corals.
  • The amount of calcium in the body can affect how fast the heart beats.
  • Some of the best sources of calcium for our bodies include dairy products like cheese, yogurt, and milk. Other sources include salmon and tofu.
  • Our bodies need vitamin D to absorb calcium.