Encyclopedia > Calcium

  Article Content


Potassium - Calcium - Scandium

Full table
Name, Symbol, NumberCalcium, Ca, 20
Series Alkali earth metals
Group, Period, Block2 (IIA), 4, s
Density, Hardness 1550 kg/m3, 1.75
Appearance silvery white
Atomic Properties
Atomic weight 40.078 amu
Atomic radius (calc.) 180 (194) pm
Covalent radius 174 pm
van der Waals radius no information
Electron configuration [Ar]4s2
e- 's per energy level2, 8, 8, 2
Oxidation states (Oxide) 2 (strong base)
Crystal structure Cubic face centered
Physical Properties
State of matter solid (paramagnetic)
Melting point 1115 K (1548F)
Boiling point 1757 K (2703F)
Molar volume 26.20 ×103 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
isoNAhalf-life DMDE MeVDP
40Ca96.941%Ca is stable with 20 neutrons
42Ca0.647%Ca is stable with 22 neutrons
43Ca0.135%Ca is stable with 23 neutrons
44Ca2.086%Ca is stable with 24 neutrons
46Ca0.004%Ca is stable with 26 neutrons
SI units & STP are used except where noted.
Calcium is a chemical element in the periodic table that has the symbol Ca and atomic number 20. Calcium is a soft grey alkaline earth metal that is used as a reducing agent in the extraction of thorium, zirconium and uranium. This element is also the fifth most abundant element in the earth's crust and is an essential element for living organisms.

Table of contents

Notable Characteristics 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. Applications 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. 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.
History (Latin calx, lime) Lime was prepared and used by the Romans as early as the 1st century, but 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. Occurrence 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. This metallic element is found in quantity in limestone, gypsum, and fluorite. Apatite is the fluorophosphate or chlorophosphate of calcium. Electrolysis of molten calcium chloride[?] (CaCl2) can be used to isolate pure calcium.
Isolation (* follow):
cathode: Ca2+* + 2e- --> Ca
anode: Cl-* --> Cl2 (gas) + e- Compounds Quicklime (CaO) 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 stalagtites[?] and stalagmites and also forms hard water[?]. Other important calcium compounds are nitrate[?], sulfide[?], chloride[?], carbide, cyanamide[?], and hypochlorite[?]. Isotopes 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.

External Links

All Wikipedia text is available under the terms of the GNU Free Documentation License

  Search Encyclopedia

Search over one million articles, find something about almost anything!
  Featured Article

... turannos. In Classical Antiquity[?] it did not always have inherently negative implications, it merely designated anyone who assumed power for any period of time ...

This page was created in 40.3 ms