Calcium Element Facts

States | Energies | Electrons | Characteristics | Reactions & Compounds | Radius | Conductivity | Abundance & Isotopes
20
Ca
40.08
Calcium
Stalactites - Mainly Calcium Carbonate.
Classification:Calcium is an alkali earth metal
Atomic weight:40.078 g/mol
Density @ 20 oC: 1.55 g/cm3
Atomic volume:29.9 cm3/mol
Roman Colosseum held together with calcium based cement.
Rome's Colosseum, resisting the ravages of time (okay, there are one or two missing pieces...) with the aid of calcium oxide based cement. Photo: David Iliff, Creative Commons Licence.


Dental amalgam.
The action of Berzelius's and then Davy's battery produced a mercury-calcium amalgam. A dental amalgam consists of 50% mercury plus mainly silver.

Discovery of Calcium


Author: Dr. Doug Stewart

Limestone [calcium carbonate] was called calx by the Romans. The Romans heated the calx, driving off carbon dioxide to leave calcium oxide. When mixed with water, calcium oxide forms cement. The Romans built vast amphitheaters and aquaducts using cement made from calx. (1)

Despite the long history of its compounds, it took the advent of electricity to first reveal the element calcium.

Calcium was first isolated by Sir Humphry Davy in 1808 in London. In a lecture to the Royal Society in June 1808, Davy describes his first experiments that year, which produced tiny amounts of metal, at best. Then a letter from Jöns Berzelius in Stockholm pointed him in the right direction. (3)

Davy learned that Berzelius and Magnus Pontin had used a battery to decompose calcium oxide at a mercury electrode and they had obtained an amalgam of mercury and calcium. (Berzelius, the great Swedish chemist, exchanged a great deal of information with Davy. Berzelius had earlier learned from Davy that potassium could be dissolved in mercury to form an amalgam. Berzelius had extended the method.) (3),(4)

Davy made a paste of slaked lime [calcium oxide, slightly moistened to form calcium hydroxide] and red oxide of mercury [mercury (II) oxide]. (3)

He made a depression in the paste and placed about 3.5 grams of mercury metal there to act as an electrode. Platinum was used as the counter electrode. Davy carried out the experiment under naptha (a liquid hydrocarbon under which he had found he could safely store potassium and sodium).

When electricity was passed through the paste, a calcium-mercury amalgam formed at the mercury electrode.

Davy removed the mercury by distillation to reveal a new, silver-white metal: calcium.

Davy used the same procedure to isolate strontium, barium, and magnesium.

He named the metal calcium because of its occurance in calx.

States

State (s, l, g): solid
Melting point: 1115 K   (842 oC)

Boiling point: 1771 K   (1484 oC)

Energies

Specific heat capacity: 0.63 J g-1 K-1
Heat of fusion: 8.54 kJ mol-1
1st ionization energy: 589.8 kJ mol-1
3rd ionization energy: 4911.8 kJ mol-1
Heat of atomization: 178 kJ mol-1
Heat of vaporization: 153.6 kJ mol-1
2nd ionization energy: 1145.4 kJ mol-1
Electron affinity: 2 kJ mol-1

Oxidation & Electrons

Shells: 2,8,8,2
Minimum oxidation number: 0
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 1
Electron configuration: 1s2 2s2 2p6 3s2 3p6 4s2
Maximum oxidation number: 2
Max. common oxidation no.: 2
Polarizability volume: 22.8 Å3

Appearance & Characteristics

Structure: ccp: cubic close packed
Hardness: 1.75 mohs

Calcium metal burning in air to form calcium nitride and calcium oxide.


Calcium metal reacting with water, producing calcium hydroxide and hydrogen gas.
Color: silvery-white


Harmful effects:
Non toxic and an essential metal for living organisms.

Characteristics:
Calcium is reactive and, for a metal, soft (with difficulty, it can be cut with a knife).

In contact with air, calcium develops a mixed oxide and nitride coating, which protects it from further corrosion.

Calcium reacts easily with water and acids and the metal burns brightly in air, forming mainly the nitride.

Uses:
Calcium forms alloys with aluminum, beryllium, copper, lead, and magnesium.

It is used in the manufacture of other metals such as uranium and thorium.

Calcium is used to remove oxygen, sulfur and carbon from alloys.

Calcium from limestone is a vital component of Portland cement.

Quicklime (CaO) is used in many applications in the chemical industry, such as treatment of drinking water - especially for water softening and arsenic removal, animal waste and wastewater.

Reactions & Compounds

Reaction with air: vigorous, ⇒ CaO, Ca3N2
Reaction with 15 M HNO3: vigorous, ⇒ H2, Ca(NO3)2
Oxide(s): CaO
Hydride(s): CaH2
Reaction with 6 M HCl: vigorous, ⇒ H2, CaCl2
Reaction with 6 M NaOH: none
Chloride(s): CaCl2

Radius

Atomic radius: 180 pm
Ionic radius (2+ ion): 114 pm
Ionic radius (2- ion): pm
Ionic radius (1+ ion): pm
Ionic radius (3+ ion): pm
Ionic radius (1- ion): pm

Conductivity

Thermal conductivity: 201 W m-1 K-1
Electrical conductivity: 0.313 x 106 S cm-1

Abundance & Isotopes

Abundance earth's crust: 4.2 % by weight , 2.2 % by moles
Abundance solar system: 70 parts per million by weight, 2 parts per million by moles
Cost, pure: $20 per 100g
Cost, bulk: $ per 100g

Source: Calcium occurs in nature in various minerals including limestone (calcium carbonate), gypsum (calcium sulfate) and fluorite (calcium fluoride). Commercially it can be made by the electrolysis of molten calcium chloride, CaCl2. The pure metal can also be produced by replacing the calcium in lime (CaCO3) with aluminum in hot, low pressure retorts.

<Isotopes:Calcium has 19 Isotopes whose half-lives are known, with mass numbers 35 to 53. Of these, five are stable: 40Ca, 42Ca, 43Ca, 44Ca and 46Ca. 97% of naturally occurring calcium is in the form of 40Ca.


References

1 The Secrets of Roman Concrete (pdf download)
2. John Davy, Memoirs of The Life of Sir Humphry Davy., Vol 1, 1836, p395, Longman.
3. John Davy (Editor), The Collected Works of Sir Humphry Davy, Vol V, 1840, p111 Smith, Elder and Co. Cornhill.
4. Jaime Wisniak, Jöns Jacob Berzelius A Guide to the Perplexed Chemist., Chem. Educator, 2000, 5, p343-350.

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