Calcium, the 20th element in the periodic table, symbolized as Ca, is called to as an essential to all living organisms. The element is known to be produced in supernova nucleosynthesis. It serves as a signal for most of the body’s cellular processes where calcium moves in and out of the cytoplasm. Calcium is the fifth most abundant element found in the Earth’s crust, and also the fifth most abundant dissolved ion, both molarity and mass, in seawater.

Physical Characteristic

Calcium, in its physical appearance is a silver-white or grey soft metal. When calcium is exposed in the air, it will instantly be coated with calcium oxide and calcium nitride, providing a grey-white color. It is highly reactive and, although soft for a metal, it is harder than lead and difficult to cut with a normal knife. The element can be usually extracted or produced using electrolysis from fusing salt like calcium chloride. In forms such as turnings or chips, it will be difficult to set fire but when lit, the metal will instantly turn into a high-intensity orange-red light.

Chemical Properties

Group 2
Period 4
Block s
Atomic number 20
State at 20°C Solid
Electron configuration [Ar] 4s2
Melting point              842°C, 1548°F, 1115 K
Boiling point   1484°C, 2703°F, 1757 K
Density (g cm−3)         1.54
Relative atomic mass 40.078
Key isotopes   40Ca
Electrochemical Equivalent 0.7477g/amp-hr
Electron Work Function 2.87eV
Electronegativity 1 (Pauling); 1.04 (Allrod Rochow)
Heat of Fusion 8.54kJ/mol
CAS number   7440-70-2

Calcium was first categorized as an ‘earth’ by Antoine Lavosier because he thought that lime or calcium oxide (produced by heating limestone and used for making plaster and mortar) is impossible to reduce further. Despite that being said, he also suspected that it must be an oxide of another unknown element.

In 1808, Humphry Davy tried reducing the lime using electrolysis just like what he did with sodium and potassium, but the experiment was a failure. Then, he tried mixing other elements such as lime and mercury oxide. The experiment was able to produce a mixture of mercury and calcium but the evidence is still not enough to confirm that he had discovered calcium. He then used more amount of lime and produced more of the amalgam in which he took off or distilles the mercury, thus, leaving only the calcium.

Calcium is the lightest among the alkaline earth metals; it is lighter in the atomic mass but is dense. It also has higher electrical resistivity than copper and aluminium and is also a better conductor. It is mostly used in terrestrial or space applications but only in low quantities because of its reactivity with air.

In our body, it is the fifth most abundant element by mass, as said above. Most are already aware that it is present in our bones as for structure. The high atomic number of the element is the reason for the bones to be radio-opaque.

Calcium is the fifth-most-abundant element by mass in the human body, where it is an important


There are five known stable isotopes of calcium. These are, 40Ca, 42Ca, 43Ca, 44Ca, 46Ca and 48Ca. Its isotope, 41Ca, is radioactive and has a very long half-life that ranges up to 103,000 years. It is produced by neutron activation the cosmogenic isotopes.

40Ca, on the other hand, is the form of the 97% of the naturally occurring calcium. It is called to as the daughter of 40K and 40Ar. Techniques using mass spectrometry and a double spike isotope dilution have been used for K-Ca age dating. 40Ca is known to have 20 protons and 20 neutrons and in comparison to the other stable isotopes of calcium, it is the heaviest with an equal amount of protons and neutrons.

Respectfully, TheWriter