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[General | States | Energies | Oxidation & Electrons]
[Appearance & Characteristics | Reactions | Other Forms]
[Radius | Conductivity
| Abundance | History]
| Name |
Calcium |
Symbol |
Ca |
| Atomic number |
20 |
Atomic weight |
40.08 |
| Density @ 293 K |
1.55 g/cm3 |
Atomic volume |
29.9 cm3/mol |
| Group |
Alkali Earth |
Discovered |
1808 |
| State (s, l, g) |
s |
| Melting point |
1112.2 K |
Boiling point |
1767 K |
| Heat of fusion |
8.540 kJ/mol |
Heat of vaporization |
153.60 kJ/mol |
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| 1st ionization energy |
589.8 kJ/mole |
Electronegativity |
1 |
| 2nd ionization energy |
1145.4 kJ/mole |
Electron affinity |
kJ/mole |
| 3rd ionization energy |
4911.8 kJ/mole |
Specific heat |
0.63 J/gK |
| Heat atomization |
178 kJ/mole atoms |
| Shells |
2,8,8,2 |
Electron configuration |
[Ar] 4s2 |
| Minimum oxidation number |
0 |
Maximum oxidation number |
2 |
| Minimum common oxidation number |
0 |
Maximum common oxidation number |
2 |
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| Structure |
hcp: hexagonal close pkd |
Color |
silvery-white |
| Uses |
lime, cement |
Toxicity |
|
| Hardness |
1.5 mohs |
Characteristics |
burns brightly |
| Reaction with air |
vigorous, =>CaO, Ca3N2 |
Reaction with 6M HCl |
vigorous, =>H2, CaCl2 |
| Reaction with 6M HCl |
vigorous, =>H2, CaCl2 |
Reaction with 15M HNO3 |
vigorous, =>H2, Ca(NO3)2 |
| Reaction with 6M NaOH |
none |
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| Number of isotopes |
6 |
Hydride(s) |
CaH2 |
| Oxide(s) |
CaO |
Chloride(s) |
CaCl2 |
| Ionic radius (2- ion) |
pm |
Ionic radius (1- ion) |
pm |
| Atomic radius |
197 pm |
Ionic radius (1+ ion) |
pm |
| Ionic radius (2+ ion) |
114 pm |
Ionic radius (3+ ion) |
pm |
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| Thermal conductivity |
201 J/m-sec-deg |
Electrical conductivity |
255.754 1/mohm-cm |
| Polarizability |
22.8 A^3 |
| Source |
Calcite (oxide) |
Rel. abund. solar system |
4.786 log |
| Abundance earth's crust |
4.65 log |
Cost, pure |
11 $/100g |
| Cost, bulk |
$/100g |
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History:
(L. calx,
lime) Though lime was prepared by the Romans in
the first century under the name calx, the metal
was not discovered until 1808. After learning
that Berzelius and Pontin prepared calcium
amalgam by electrolyzing lime in mercury, Davy
was able to isolate the impure metal. Calcium is
a metallic element, fifth in abundance in the
earth's crust, of which if forms more than 3%. It
is an essential constituent of leaves, bones,
teeth, and shells. Never found in nature
uncombined, it occurs abundantly as limestone,
gypsum, and fluorite; apatite is the
fluorophosphate or chlorophosphate of calcium.
The metal has a silvery color, is rather hard,
and is prepared by electrolysis of the fused
chloride to which calcium fluoride is added to
lower the melting point. Chemically it is one of
the alkaline earth elements; it readily forms a
white coating of nitride in air, reacts with
water, burns with a yellow-red flame, forming
largely the nitride. The metal is used as a
reducing agent in preparing other metals such as
thorium, uranium, zirconium, etc., and is used as
a deoxidizer, desulfurizer, or decarburizer for
various ferrous and nonferrous alloys. It is also
used as an alloying agent for aluminum,
beryllium, copper, lead, and magnesium alloys,
and serves as a "getter" for residual
gases in vacuum tubes, etc. Its natural and
prepared compounds are widely used. Quicklime
(CaO), made by heating limestone and changed into
slaked lime by the careful addition of water, is
the great cheap base of chemical refinery with
countless uses. Mixed with sand it hardens as
mortar and plaster by taking up carbon dioxide
from the air. Calcium from limestone is an
important element in Portland cement. The
solubility of the carbonate in water containing
carbon dioxide causes the formation of caves with
stalactites and stalagmites and is responsible
for hardness in water. Other important compounds
are the carbide, chloride, cyanamide,
hypochlorite, nitrate, and sulfide.
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