Calcium

potassium ← calcium → scandium

Mg
↑
Ca
↓
Sr

periodic table

General

Name, Symbol, Number

calcium, Ca, 20

Chemical series

alkaline earth metals

Group, Period, Block

2, 4, s

Appearance

silvery white

Atomic mass

40.078 (4) g/mol

Electron configuration

[Ar] 4s²

Electrons per shell

2, 8, 8, 2

Physical properties

Phase

solid

Density (near r.t.)

1.55 g/cm³

Liquid density at m.p.

1.378 g/cm³

Melting point

1115 K
(842 ° C, 1548 ° F)

Boiling point

1757 K
(1484 ° C, 2703 ° F)

Heat of fusion

8.54 kJ/mol

Heat of vaporization

154.7 kJ/mol

Heat capacity

(25 °C) 25.929 J/(mol·K)

Vapor pressure
P/Pa	1	10	100	1 k	10 k	100 k
at T/K	864	956	1071	1227	1443	1755

Atomic properties

Crystal structure

cubic face centered

Oxidation states

2
(strongly basic oxide)

Electronegativity

1.00 ( Pauling scale)

Ionization energies
( more)

1st: 589.8 kJ/mol

2nd: 1145.4 kJ/mol

3rd: 4912.4 kJ/mol

Atomic radius

180 pm

Atomic radius (calc.)

194 pm

Covalent radius

174 pm

Miscellaneous

Magnetic ordering

paramagnetic

Electrical resistivity

(20 °C) 33.6 nΩ·m

Thermal conductivity

(300 K) 201 W/(m·K)

Thermal expansion

(25 °C) 22.3 µm/(m·K)

Speed of sound (thin rod)

(20 °C) 3810 m/s

Young's modulus

20 GPa

Shear modulus

7.4 GPa

Bulk modulus

17 GPa

Poisson ratio

0.31

Mohs hardness

1.75

Brinell hardness

167 MPa

CAS registry number

7440-70-2

Notable isotopes

Main article: Isotopes of calcium
iso	NA	half-life	DM	DE ( MeV)	DP
⁴⁰Ca	96.941%	Ca is stable with 20 neutrons
⁴¹Ca	syn	1.03×10⁵ y	ε	-	⁴¹K
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
⁴⁵Ca	syn	162.7 d	β^-	0.258	⁴⁵ Sc
⁴⁶Ca	0.004%	>2.8×10¹⁵ y	β^-β^-	?	⁴⁶ Ti
⁴⁷Ca	syn	4.536 d	β^-	0.694, 1.99	⁴⁷ Sc
⁴⁷Ca	syn	4.536 d	γ	1.297	-
⁴⁸Ca	0.187%	>4×10¹⁹ y	β^-β^-	?	⁴⁸ Ti

References

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. Calcium is also the fifth most abundant element in the earth's crust. It is essential for living organisms, particularly in cell physiology, and is the most common metal in many animals.

Notable characteristics

Calcium is a rather soft, metallic element that is purified by electrolysis from calcium fluoride. It 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 essential in muscle contraction, building strong bones and teeth, blood clotting, nerve impulse transmission, regulating heartbeat, and fluid balance within cells.

50%-75% of calcium comes from the dairy intake in daily diets.
Most Americans do not consume the 1,200 mg of calcium per day that is needed.

The Calcium-40 isotope has a nucleus of 20 Protons and 20 Neutrons. Calcium has 20 electrons distributed as follows: 2 in the K shell (principal quantum number 1), 8 in the L shell (principal quantum number 2), 8 in the M shell (principal quantum number 3), and 2 in the N shell (principal quantum number 4). The outer shell is the valence shell, with 2 electrons in the lone 4s orbital, the 3 p orbitals being empty. See also electron configuration..

Calcium cannot be found alone in nature. Calcium is found mostly as limestone, gypsum and fluorite. Stalagmites and stalactites contain calcium carbonate.

Applications

Calcium is an important component of a healthy diet. Its minor deficit can affect bone and teeth formation, while overretention can cause kidney stones. Vitamin D is needed to absorb calcium. Dairy products, such as milk and cheese, are a well known source of calcium. However, some individuals are allergic to dairy products and even more people, particularly those of non-European descent, are lactose-intolerant, leaving them unable to consume dairy products. Fortunately, many other good sources of calcium exist. This includes seaweeds such as kelp, wakame and hijiki; nuts and seeds (like almonds and sesame), beans; seafood such as oysters and shrimp; soft-boned fish; amaranth; whole wheat; collard greens; okra; rutabaga; broccoli; and fortified products such as orange juice and bread.

For more information about Ca in living nature, see calcium in biology and calcium metabolism.

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 aluminium, beryllium, copper, lead, and magnesium alloys.
Removing ice on the streets and on the sidewalks in North America.
It is also used in making cements and mortar that are used in building.

History

Calcium ( Latin calx, meaning "lime") was known of as early as the first century when the Ancient Romans prepared lime as calcium oxide. It was not actually isolated until 1808 in England when Sir Humphrey Davy electrolyzed a mixture of lime and mercuric oxide. Davy was trying to isolate calcium and when he heard that Berzelius and Pontin prepared calcium amalgam by electrolyzing lime in mercury, he tried it himself. He worked with electrolysis throughout his life and also discovered/isolated magnesium, strontium and barium.

Compounds

Calcium, combined with phosphate to form hydroxylapatite, is the mineral portion of human and animal bones and teeth. The mineral portion of some corals can also be transformed into hydroxylapatite.

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 dissolves 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.

Isotopes

Calcium has four stable isotopes (Ca-40 and Ca-42 through Ca-44), plus two more isotopes (Ca-46 and Ca-48) that have such long half-lives that for all practical purposes they can be considered stable. It also has a cosmogenic isotope, radioactive Ca-41, which has a half-life = 103,000 years. 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 metre 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.

Naturally occurring calcium is 97% 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.