What is Calcium?

Calcium is an alkaline earth metal. Group 2 elements of the modern periodic table are known as alkaline earth metals(except Beryllium). Calcium being an alkaline earth metal, it forms a dark oxide-nitrate layer due to its high reactivity and when exposed to the air. Its physical and chemical properties are most similar to its heavier homologs strontium and barium. Sir Humphry Davy discovered calcium in 1808. Calcium is found to be the most abundant metal and when talking about the human body it is the fifth most abundant element in the human body. In physiological and biochemical processes of organisms and cells, calcium ions have an important role as electrolytes. There are various uses of calcium and it is one of the most important chemical elements.

Calcium Element

The chemical symbol of calcium is 'Ca'.Its atomic number is 20 and its atomic mass is 40.078 g/mol.

The location of calcium element in modern periodic table is the 2nd group,4th period, and 's' block. Its electronic configuration is [Ar]4s². At 20°c, this element is present in solid-state. It has a melting point of 842°c and a boiling point of 1484°c. The density of calcium is 1.54 gm/cm³.Important isotopes of calcium include 48Ca, 46Ca, 44Ca, 43Ca, 42Ca, and 40Ca.CAS number for calcium is 7440-70-2.

Calcium Symbol

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Atomic Structure of Calcium

The nuclear composition of an atom of calcium-40 (atomic number: 20), the most common isotope of this element consists of 20 protons and 20 neutrons. 20 electrons occupy available electron shells (rings).

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Number of Energy Levels: 4

First Energy Level: 2 

Second Energy Level: 8 

Third Energy Level: 8 

Fourth Energy Level: 2

So we can see it has 2 electrons in its valence shell, hence its valency is 2.The crystal structure of calcium is cubic. The atomic data of calcium is as follows:

Covalent radius (Å) :  1.74

Electron affinity       :  2.369 (kJ mol−1)

Electronegativity     :  1.00 (Pauling scale)

Atomic Data of Calcium

Atomic radius, non-bonded (Å)


Covalent radius (Å)


Electron affinity (kJ mol−1)


Electronegativity (Pauling scale)


Ionisation Energies (kJ mol−1)

















Uses of Calcium

  1. The biological use of calcium is to provide strength and structure to the skeleton. It is vital for the maintenance of bones and teeth.

  2. Calcium ions on bone surfaces interact with those present in the bodily fluids, therefore enabling ion exchange, which is essential in maintaining the balance of calcium in the blood and bone.

  3. Calcium circulating in the blood is involved in several vital processes including coagulation, nerve signal transmission, hormone signalling, and muscle contraction.

  4. Calcium may be used as a reducing agent in the process of metal extraction.

  5. Calcium is also used in the production of some metals, as an alloying agent.

  6. Calcium carbonate is used to make cement and mortar and also in the glass industry.

Properties of Calcium

Properties of calcium can be categorised as physical and chemical.

Physical Properties of Calcium

These are those properties that can be observed using our senses such as colour, lustre, freezing point, boiling point, melting point, density, hardness, and odour. These are observed without changing the substance into another substance. They are:

  1. Colour: Silvery-white metallic

  2. Phase: Solid

  3. Hardness: Relatively soft metal

  4. Crystalline structure: Cubic

  5. Ductility: It can be beaten into extremely thin sheets. It can be pressed, rolled, and cut

  6. Malleability: Capable of being shaped or bent

  7. Melting point: Melting point is 842°C

  8. Boiling point: Boiling point is 1484°C

Chemical Properties of Calcium

These are only observable during a chemical reaction. These properties determine how calcium behaves when changing from one substance to another or when reacting with other substances. They are:

  1. Chemical Formula: Ca

  2. Oxidation: Used as a deoxidizer in steel

  3. Isotopes: Six

  4. Compounds: Compounds include limestone, marble, gypsum, etc.

  5. Flammability: When heated in air or in oxygen it ignites

  6. Reactivity with water: Reacts with cold water rapidly at first, but the reaction is then slowed due to the formation of a film of Calcium hydroxide - Ca(OH)2

  7. Reactivity with acids: Highly reactive

Calcium Compounds

Important compounds of calcium are:

  1. Calcium oxide or Quicklime (CaO)

  2. Calcium hydroxide or Slaked lime (Ca(OH)2)

  3. Calcium Carbonate (CaCO3)

  4. Calcium Sulphate or Plaster of Paris (CaSO4 . 1/2H2O)

Facts About Calcium

  1. Humans have known about calcium and its compounds before Greeks and Romans.

  2. Romans made use of lime in their concrete and termed it “Calx.”

  3. Davy could separate pure calcium in 1808. He was the original chemist to do so.

  4. It turns tougher as a silver-coloured metal once it is refined.

  5. Calcium is used in fireworks to add orange colour.

FAQ (Frequently Asked Questions)

1. What Diet Should We Take to Increase Calcium in Our Bodies?

  1. Include dairy products in your diet every day. Choose from milk, yoghurt, cheese, or milk-based custard.

  2. Leafy green vegetables as broccoli, cabbage, spinach should be eaten every day.

  3. Eat more fish. In absence of fresh fish, tinned fish such as sardines or salmon with the bones left in should be eaten.

  4. Calcium-rich nuts like Brazil nuts or almonds should be taken as snacks.

  5. Reduce your intake of caffeine, soft drinks, and alcohol asl calcium absorption is inhibited by them and should be used in moderation.

  6. Sprinkle sesame seeds over vegetables or salads. Sesame seeds are easily available to be a part of all meals and are high in calcium.

2. How Do You Remove Calcium From Water Naturally?

To treat the water all it takes is some sodium carbonate or washing soda. Adding this in hard water breaks down and removes calcium and magnesium from the water supply. Pipes are protected by chemical treatment and treatment process is safe when used as intended. Calcium is naturally present in water. It may dissolve from rocks such as limestone, marble, calcite, dolomite, gypsum, fluorite and apatite. Calcium determines water hardness, because of its presence in water as Ca2+ ions.