|Name, Symbol, Number||Calcium, Ca, 20|
|Series ||Alkaline earth metal|
|Group, Period, Block||2 (IIA), 4, s|
|Density, Hardness ||1550 kg/m3, 1.75|
|Appearance ||silvery white|
|Atomic weight ||40.078 amu|
|Atomic radius (calc.) ||180 (194) pm|
|Covalent radius ||174 pm|
|van der Waals radius ||no information |
|Electron configuration ||[Ar]4s4s2|
|e- 's per energy level||2, 8, 8, 2|
|Oxidation states (Oxide) ||2 (strong base)|
|Crystal structure ||Cubic face centered|
|State of matter ||solid (paramagnetic)|
|Melting point ||1115 K (1548°F) |
|Boiling point ||1757 K (2703°F)|
|Molar volume ||26.20 ×10103 m3/mol|
|Heat of vaporization ||153.6 kJ/mol|
|Heat of fusion ||8.54 kJ/mol|
|Vapor pressure ||254 Pa at 1112 K|
|Speed of sound ||3810 m/s at 293.15 K|
|Electronegativity ||1.00 (Pauling scale) |
|Specific heat capacity ||0.632 J/(kg*K)|
|Electrical conductivity ||29.8 106/m ohm|
|Thermal conductivity ||201 W/(m*K)|
|1st ionization potential ||589.8 kJ/mol|
|2nd ionization potential ||1145.4 kJ/mol|
|3rd ionization potential ||4912.4 kJ/mol|
|Most Stable Isotopes|
|iso||NA||half-life ||DM||DE MeV||DP|
|40Ca||96.941%||Ca is stable with 20 neutrons|
|42Ca||0.647%||Ca is stable with 22 neutrons
|43Ca||0.135%||Ca is stable with 23 neutrons|
|44Ca||2.086%||Ca is stable with 24 neutrons|
|46Ca||0.004%||Ca is stable with 26 neutrons|
|SI units & STP are used except where noted.
is a chemical element
in the periodic table
that has the symbol Ca and atomic number
Calcium is a soft grey alkaline earth metal
that is used as a reducing
agent in the extraction of
. This element is also the fifth most abundant element in the earth's crust. It is essential for living organisms, particularly in cell physiology.
Calcium is a rather hard element that is purified by electrolysis from calcium fluoride that burns with a yellow-red flame and forms a white nitride coating when exposed to air. It reacts with water displacing hydrogen and forming calcium hydroxide.
Calcium is an important component of a healthy diet. Its minor deficit can affect bone and teeth formation. Its excess can lead to kidney stones. Vitamin D is needed to absorb calcium. Dairy products are an excellent source of calcium.
For more information about Ca in living nature see Ca (biology)
Other uses include:
- Reducing agent in the extraction of other metals such as uranium, zirconium, and thorium.
- Deoxidizer, desulfurizer, or decarburizer for various ferrous and nonferrous alloys.
- Alloying agent used in the production of aluminum, beryllium, copper, lead, and magnesium alloys.
) Lime was prepared and used by the Romans as early as the 1st century
calcium was not discovered until 1808
. After learning that Berzelius
and Pontin prepared calcium amalgam
by electrolyzing lime in mercury
, Sir Humphry Davy
was able to isolate the impure metal.
Calcium is the fifth most abundant element in the earth's crust (forming more than 3%) and is an essential part of leaves, bones, teeth, and shells. Due to its chemical reactivity with air and water, calcium is never found in nature unbound to other elements, except in living organisms where Ca2+ plays a key role in cell physiology. This metallic element is found in quantity in limestone
, and fluorite
is the fluorophosphate or chlorophosphate of calcium. Electrolysis
of molten calcium chloride
) can be used to isolate pure calcium.
* + 2e-
* --> ½Cl2
) + e-
) is used in many chemical refinery processes and is made by heating and carefully adding water to limestone
. When CaO is mixed with sand it hardens into a mortar
and is turned into plaster
by carbon dioxide
uptake. Mixed with other compounds, CaO forms an important part of Portland cement
When water percolates through limestone or other soluble carbonate rocks, it partially disolves part of the rock and causes cave formation and characteristic stalactites and stalagmites and also forms hard water. Other important calcium compounds are nitrate, sulfide, chloride, carbide, cyanamide, and hypochlorite.
Calcium has six stable isotopes, two of which occur in nature: stable Ca-40 and radioactive Ca-41 with a half-life = 103,000 years. 97% of the element is in the form of Ca-40. Ca-40 is one of the daughter products of K-40 decay, along with Ar-40. While K-Ar dating has been used extensively in the geological sciences, the prevalence of Ca-40 in nature has impeded its use in dating. Techniques using mass spectrometry and a double spike isotope dilution have been used for K-Ca age dating. Unlike cosmogenic isotopes that are produced in the atmosphere, Ca-41 is produced by neutron activation of Ca-40. Most of its production is in the upper meter or so of the soil column where the cosmogenic neutron flux is still sufficiently strong. Ca-41 has received much attention in stellar studies because Ca-41 decays to K-41, a critical indicator of solar-system anomalies.