Post by chenhongxia on Apr 30, 2009 11:05:25 GMT 7
Talk about Calcium
For other uses, see Calcium (disambiguation).
20 potassium ¡û calcium ¡ú scandium
Mg
¡ü
Ca
¡ý
Sr
Periodic table - Extended periodic table
General
Name, symbol, number calcium, Ca, 20
Chemical series alkaline earth metals
Group, period, block 2, 4, s
Appearance silvery white
Standard atomic weight 40.078(4)?g¡¤mol?1
Electron configuration [Ar] 4s2
Electrons per shell 2, 8, 8, 2
Physical properties
Phase solid
Density (near r.t.) 1.55 g¡¤cm?3
Liquid density at m.p. 1.378 g¡¤cm?3
Melting point 1115 K
(842 ¡ãC, 1548 ¡ãF)
Boiling point 1757 K
(1484 ¡ãC, 2703 ¡ãF)
Heat of fusion 8.54 kJ¡¤mol?1
Heat of vaporization 154.7 kJ¡¤mol?1
Specific heat capacity (25 ¡ãC) 25.929 J¡¤mol?1¡¤K?1
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 face centered cubic
Oxidation states 2
(strongly basic oxide)
Electronegativity 1.00 (Pauling scale)
Ionization energies
(more) 1st: 589.8 kJ¡¤mol?1
2nd: 1145.4 kJ¡¤mol?1
3rd: 4912.4 kJ¡¤mol?1
Atomic radius 180 pm
Atomic radius (calc.) 194 pm
Covalent radius 174 pm
Miscellaneous
Magnetic ordering paramagnetic
Electrical resistivity (20 ¡ãC) 33.6 n¦¸¡¤m
Thermal conductivity (300 K) 201 W¡¤m?1¡¤K?1
Thermal expansion (25 ¡ãC) 22.3 ¦Ìm¡¤m?1¡¤K?1
Speed of sound (thin rod) (20 ¡ãC) 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
Selected isotopes
Main article: Isotopes of calcium iso NA half-life DM DE (MeV) DP
40Ca 96.941% 40Ca is stable with 20 neutrons
41Ca syn 1.03¡Á105 y ¦Å - 41K
42Ca 0.647% 42Ca is stable with 22 neutrons
43Ca 0.135% 43Ca is stable with 23 neutrons
44Ca 2.086% 44Ca is stable with 24 neutrons
45Ca syn 162.7 d ¦Â- 0.258 45Sc
46Ca 0.004% >2.8¡Á1015 y ¦Â-¦Â- ? 46Ti
47Ca syn 4.536 d ¦Â- 0.694, 1.99 47Sc
¦Ã 1.297 -
48Ca 0.187% >4¡Á1019 y ¦Â-¦Â- ? 48Ti
References
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Calcium (pronounced /?k?lsi?m/) is the chemical element with the symbol Ca and atomic
number 20. It has an atomic mass of 40.078. Calcium is a soft grey alkaline earth metal,
and is the fifth most abundant element by mass in the Earth's crust. Calcium is also the
fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium,
chloride, magnesium, and sulfate.[1]
Calcium is essential for living organisms, particularly in cell physiology, where
movement of the calcium ion Ca2+ into and out of the cytoplasm functions as a signal for
many cellular processes. As a major material used in mineralization of bones and shells,
calcium is the most abundant metal by mass in many animals.
characteristics
Chemically calcium is reactive and soft for a metal (though harder than lead, it can be
cut with a knife with difficulty). It is a silvery metallic element that must be
extracted by electrolysis from a fused salt like calcium chloride.[2] Once produced, it
rapidly forms a grey-white oxide and nitride coating when exposed to air. It is somewhat
difficult to ignite, unlike magnesium, but when lit, the metal burns in air with a
brilliant high-intensity red light. Calcium metal reacts with water, evolving hydrogen
gas at a rate rapid enough to be noticeable, but not fast enough at room temperature to
generate much heat. In powdered form, however, the reaction with water is extremely
rapid, as the increased surface area of the powder accelerates the reaction with the
water. Part of the slowness of the calcium-water reaction results from the metal being
partly protected by insoluble white calcium hydroxide. In water solutions of acids where
the salt is water soluble, calcium reacts vigorously.
Calcium, though it has a higher resistivity than copper or aluminium, weight for weight,
allowing for its much lower density calcium is a rather better conductor than either.
However, its use in terrestrial applications is usually limited by its high reactivity
with air. In vacuum use, calcium tends to sublime unless plated.
Calcium saltshttp://www.lookchem.com/cas-590/5902-95-4.html are colorless from any
contribution of the calcium, and ionic solutions of calcium (Ca2+) are colorless as well.
Many calcium salts are not soluble in water. When in solution, the calcium ion to the
human taste varies remarkably, being reported as mildly salty, sour, "mineral like" or
even "soothing." It is apparent that many animals can taste, or develop a taste, for
calcium, and use this sense to detect the mineral in salt licks or other sources.[3] In
human nutrition, soluble calcium salts may be added to tart juices without much effect to
the average palate.
Calcium is the fifth most abundant element by mass in the human body, where it is a
common cellular ionic messenger with many functions, and serves also as a structural
element in bone. It is the relatively high atomic-numbered calcium in the skeleton which
causes bone to be radio-opaque. Of the human body's solid components after drying (as for
example, after cremation), about a third of the total mass is the approximately one
kilogram of calcium which composes the average skeleton (the remainder being mostly
phosphorus and oxygen).
For other uses, see Calcium (disambiguation).
20 potassium ¡û calcium ¡ú scandium
Mg
¡ü
Ca
¡ý
Sr
Periodic table - Extended periodic table
General
Name, symbol, number calcium, Ca, 20
Chemical series alkaline earth metals
Group, period, block 2, 4, s
Appearance silvery white
Standard atomic weight 40.078(4)?g¡¤mol?1
Electron configuration [Ar] 4s2
Electrons per shell 2, 8, 8, 2
Physical properties
Phase solid
Density (near r.t.) 1.55 g¡¤cm?3
Liquid density at m.p. 1.378 g¡¤cm?3
Melting point 1115 K
(842 ¡ãC, 1548 ¡ãF)
Boiling point 1757 K
(1484 ¡ãC, 2703 ¡ãF)
Heat of fusion 8.54 kJ¡¤mol?1
Heat of vaporization 154.7 kJ¡¤mol?1
Specific heat capacity (25 ¡ãC) 25.929 J¡¤mol?1¡¤K?1
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 face centered cubic
Oxidation states 2
(strongly basic oxide)
Electronegativity 1.00 (Pauling scale)
Ionization energies
(more) 1st: 589.8 kJ¡¤mol?1
2nd: 1145.4 kJ¡¤mol?1
3rd: 4912.4 kJ¡¤mol?1
Atomic radius 180 pm
Atomic radius (calc.) 194 pm
Covalent radius 174 pm
Miscellaneous
Magnetic ordering paramagnetic
Electrical resistivity (20 ¡ãC) 33.6 n¦¸¡¤m
Thermal conductivity (300 K) 201 W¡¤m?1¡¤K?1
Thermal expansion (25 ¡ãC) 22.3 ¦Ìm¡¤m?1¡¤K?1
Speed of sound (thin rod) (20 ¡ãC) 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
Selected isotopes
Main article: Isotopes of calcium iso NA half-life DM DE (MeV) DP
40Ca 96.941% 40Ca is stable with 20 neutrons
41Ca syn 1.03¡Á105 y ¦Å - 41K
42Ca 0.647% 42Ca is stable with 22 neutrons
43Ca 0.135% 43Ca is stable with 23 neutrons
44Ca 2.086% 44Ca is stable with 24 neutrons
45Ca syn 162.7 d ¦Â- 0.258 45Sc
46Ca 0.004% >2.8¡Á1015 y ¦Â-¦Â- ? 46Ti
47Ca syn 4.536 d ¦Â- 0.694, 1.99 47Sc
¦Ã 1.297 -
48Ca 0.187% >4¡Á1019 y ¦Â-¦Â- ? 48Ti
References
This box: view ? talk ? edit
Calcium (pronounced /?k?lsi?m/) is the chemical element with the symbol Ca and atomic
number 20. It has an atomic mass of 40.078. Calcium is a soft grey alkaline earth metal,
and is the fifth most abundant element by mass in the Earth's crust. Calcium is also the
fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium,
chloride, magnesium, and sulfate.[1]
Calcium is essential for living organisms, particularly in cell physiology, where
movement of the calcium ion Ca2+ into and out of the cytoplasm functions as a signal for
many cellular processes. As a major material used in mineralization of bones and shells,
calcium is the most abundant metal by mass in many animals.
characteristics
Chemically calcium is reactive and soft for a metal (though harder than lead, it can be
cut with a knife with difficulty). It is a silvery metallic element that must be
extracted by electrolysis from a fused salt like calcium chloride.[2] Once produced, it
rapidly forms a grey-white oxide and nitride coating when exposed to air. It is somewhat
difficult to ignite, unlike magnesium, but when lit, the metal burns in air with a
brilliant high-intensity red light. Calcium metal reacts with water, evolving hydrogen
gas at a rate rapid enough to be noticeable, but not fast enough at room temperature to
generate much heat. In powdered form, however, the reaction with water is extremely
rapid, as the increased surface area of the powder accelerates the reaction with the
water. Part of the slowness of the calcium-water reaction results from the metal being
partly protected by insoluble white calcium hydroxide. In water solutions of acids where
the salt is water soluble, calcium reacts vigorously.
Calcium, though it has a higher resistivity than copper or aluminium, weight for weight,
allowing for its much lower density calcium is a rather better conductor than either.
However, its use in terrestrial applications is usually limited by its high reactivity
with air. In vacuum use, calcium tends to sublime unless plated.
Calcium saltshttp://www.lookchem.com/cas-590/5902-95-4.html are colorless from any
contribution of the calcium, and ionic solutions of calcium (Ca2+) are colorless as well.
Many calcium salts are not soluble in water. When in solution, the calcium ion to the
human taste varies remarkably, being reported as mildly salty, sour, "mineral like" or
even "soothing." It is apparent that many animals can taste, or develop a taste, for
calcium, and use this sense to detect the mineral in salt licks or other sources.[3] In
human nutrition, soluble calcium salts may be added to tart juices without much effect to
the average palate.
Calcium is the fifth most abundant element by mass in the human body, where it is a
common cellular ionic messenger with many functions, and serves also as a structural
element in bone. It is the relatively high atomic-numbered calcium in the skeleton which
causes bone to be radio-opaque. Of the human body's solid components after drying (as for
example, after cremation), about a third of the total mass is the approximately one
kilogram of calcium which composes the average skeleton (the remainder being mostly
phosphorus and oxygen).