Calcium Facts – Atomic Number 20 and Element Symbol Ca

Calcium is the 20^th element of the periodic table. These calcium facts contain chemical and physical data along with general information and history.

Calcium periodic table cell

Basic Calcium Facts

Name: Calcium

Atomic Number: 20

Element Symbol: Ca

Group: 2

Period: 4

Block: s

Element Family: Alkaline Earth

Atomic Mass: 40.078(4)

Electron Configuration: [Ar]4s²
Full: 1s²2s²2p⁶3s²3p⁶4s² (full)

Discovery: Sir Humphry Davy in 1808

Davy is well known for his electrolysis experiments. He would place his instrument in samples of various common chemicals and observe what collects at the electrodes. He isolated pure calcium from a paste of lime (calcium oxide) using a mercury electrode. An solid amalgam of calcium and mercury formed when current was applied. Davy then used chemical techniques to remove the mercury and solid calcium remained.

Name Origin: Calcium got its name from the Latin name for lime, calx.

Isotopes:

Natural calcium is comprised of six isotopes: ⁴⁰Ca, ⁴²Ca, ⁴³Ca, ⁴⁴Ca, ⁴⁶Ca, and ⁴⁸Ca.
Five stable and nineteen radioactive isotopes exist ranging from ³⁴Ca to ⁵⁷Ca.

⁴⁰Ca
Calcium-40 is a stable isotope containing 20 neutrons. 96.941% of natural calcium is calcium-40. Calcium-40 is theorized to actually be a radioactive isotope with an extremely long half-life (~10²¹ years) based on its internal structure. No one has ever detected a decay of a calcium-40 atom.

⁴²Ca
Calcium-42 is a stable isotope containing 22 neutrons. 0.647% of natural calcium is calcium-42.

⁴³Ca
Calcium-43 is a stable isotope containing 23 neutrons. 0.135% of natural calcium is calcium-43.

⁴⁴Ca
Calcium-44 is a stable isotope containing 24 neutrons. 2.086% of natural calcium is calcium-44.

⁴⁶Ca
Calcium-46 is a stable isotope containing 26 neutrons. 0.004% of natural calcium is calcium-46.
As with calcium-40, the internal structure of the calcium-46 atom is theoretically unstable and could be radioactive. No one has ever observed the decay of a calcium-46 atom.

⁴⁸Ca
Calcium-48 is almost a stable isotope containing 28 neutrons. Calcium-48 has been observed to decay into titanium-48 by double β- decay. The half-life of this decay has been calculated to 3.338 x 10²¹ years. This decay makes calcium-48 the lightest isotope to undergo double β- decay. 0.187% of natural calcium is calcium-48.

Calcium Metal (Tomihahndorf)

Physical Data

Density:  1.54 g/cm³

Melting Point: 1115 K ​(842 °C, ​1548 °F)

Boiling Point: 1757 K ​(1484 °C, ​2703 °F)

State at 20ºC: Solid

Heat of Fusion: 8.54 kJ/mol

Heat of Vaporization: 154.7 kJ/mol

Molar Heat Capacity: 25.929 J/mol·K

Electron shell configuration for calcium.

Atomic Data

Atomic Radius: 1.97 Å (empirical)

Covalent Radius: 1.76 Å

Van der Waals Radius:  2.31 Å

Electron Affinity: 2.369 kJ/mol

Electronegativity: 1.00

1^st Ionization Energy: 589.83 kJ/mol

2^nd Ionization Energy: 1145.447 kJ/mol

3^rd Ionization Energy: 4912.368 kJ/mol

4^th Ionization Energy: 5876.92 kJ/mol

5^th Ionization Energy: 8153 kJ/mol

6^th Ionization Energy: 10495.68 kJ/mol

7^th Ionization Energy: 12272.9 kJ/mol

8^th Ionization Energy: 14206.5 kJ/mol

Oxidation States: +2 (common), +1, -1 (uncommon)

Calcium flame test. Credit: Herge/Creative Commons

Fun Calcium Facts

• Calcium is a soft silvery metal at room temperature. Left alone, it will quickly oxidize in air forming a dull grey patina.
• Calcium burns with a bright orange-red flame in a flame test.
• Calcium is used in fireworks to add orange color.
• Calcium is the fifth most abundant element in the human body. Nearly all the calcium in your body is in your teeth and bones.
• Vitamin D is vital for the absorption of calcium in your body.
• Calcium is the fifth most abundant element in the Earth’s crust, accounting for approximately 4.1% by mass.
• Calcium is not found native in nature. It is always part of another compound.
• Sea creature shells are mostly calcium carbonate.
• Calcium can be found abundantly in limestone (calcium carbonate), gypsum (calcium sulfate), fluorite (calcium fluoride) and apatite (calcium-chloro-( or fluoro-) phosphate.
• Calcium is produced commercially by heating lime (calcium oxide) with aluminum in a low pressure environment.
• Calcium is used for making cement, making cheese, removing nonmetallic impurities from alloys, and as a reduction agent in the preparation of other metals.
• Calcium was known to exist for centuries before Davy identified it as an element.

Learn more about elements on the periodic table.