Calcium (Ca)


  • Symbol: Ca
  • Atomic Number: 20
  • Atomic Weight: 40.078
  • Element Classification: Alkaline Earth Metal
  • Discovered By: Sir Humphry Davy
  • Discovery Date: 1808
  • Name Origin: Latin: ‘calx’ (lime)
  • Density(g/cc): 1.55 (at 20°C)
  • Melting Point: 842°C
  • Boiling Point: 1484°C
  • Appearance: Silvery-white, soft metal
  • Atomic Radius(pm): 194


Calcium was isolated by Sir Humphry Davy in 1808, shortly after his discovery of potassium and sodium. Davy used electrolysis to extract calcium from a mixture of lime (CaO) and mercuric oxide (HgO), revealing the metal. The name “calcium” derives from the Latin word ‘calx’, meaning lime, which has been known and used since ancient times for various purposes, including construction and as a material in the production of other metals.

Relation to Other Elements

Calcium is a member of the alkaline earth metals group in the periodic table. These elements are characterized by their two electrons in the outer shell, which they readily lose to form cations with a +2 charge. Calcium’s chemical behavior is similar to its group neighbors, such as magnesium (Mg) and strontium (Sr), but it is less reactive than the alkali metals. Calcium compounds, especially calcium carbonate (CaCO₃) and calcium phosphate (Ca₃(PO₄)₂), play vital roles in biological systems and geological formations.

Natural Occurrence

Calcium is the fifth most abundant element in the Earth’s crust and is a significant component of the human body, primarily found in bones and teeth in the form of calcium phosphate. In nature, calcium is never found in its elemental state due to its reactivity but is abundant in minerals such as limestone, gypsum, and fluorite. The Earth’s crust and oceans contain vast amounts of calcium, which is essential for the life processes of all plants and animals.


Calcium has a variety of important applications:

  • Construction: Calcium compounds, like calcium carbonate (limestone) and calcium hydroxide (lime), are used in the construction industry for cement and mortar.
  • Metallurgy: Calcium is used as a reducing agent in the extraction of other metals, such as uranium and thorium.
  • Chemicals: Calcium salts are used in a variety of products, including plastics, paper, paint, and food as stabilizers, fillers, and colorants.
  • Water Treatment: Calcium hydroxide is used in water treatment to adjust pH and soften water.
  • Dietary Supplement: Calcium is crucial for human health, particularly for bone and tooth formation. It is often taken as a dietary supplement to prevent osteoporosis.

The discovery of calcium and its subsequent applications in construction, metallurgy, chemistry, and health have made it a cornerstone of modern industry and essential for biological life. Calcium’s widespread presence in the Earth’s crust and its biological importance underscore its significance across various fields of science and industry.

Potassium (K)

Scandium (Sc)