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{{Elementbox
|name=calcium
|pronounce={{IPAc-en|ˈ|k|æ|l|s|i|ə|m}} {{respell|KAL|see-əm}}
|number=20
|symbol=Ca
|left=[[potassium]]
|right=[[scandium]]
|above=[[magnesium|Mg]]
|below=[[strontium|Sr]]
|series=alkaline earth metal
|series comment=
|group=2
|period=4
|block=s
|series color=
|phase color=
|appearance=dull gray, silver
|image name=Calcium unter Argon Schutzgasatmosphäre.jpg
|image size=
|image name comment=
|image name 2=Calcium Spectrum.png
|image name 2 comment=Spectral lines of calcium
|atomic mass=40.078
|atomic mass 2=4
|atomic mass comment=
|electron configuration=[[[argon|Ar]]] 4s<sup>2</sup>
|electrons per shell=2, 8, 8, 2
|color=
|phase=solid
|phase comment=
|density gplstp=
|density gpcm3nrt=1.55
|density gpcm3nrt 2=
|density gpcm3mp=1.378
|melting point K=1115
|melting point C=842
|melting point F=1548
|boiling point K=1757
|boiling point C=1484
|boiling point F=2703
|triple point K=
|triple point kPa=
|critical point K=
|critical point MPa=
|heat fusion=8.54
|heat fusion 2=
|heat vaporization=154.7
|heat capacity=25.929
|vapor pressure 1=864
|vapor pressure 10=956
|vapor pressure 100=1071
|vapor pressure 1 k=1227
|vapor pressure 10 k=1443
|vapor pressure 100 k=1755
|vapor pressure comment=
|crystal structure=face-centered cubic
|oxidation states='''+2''', +1<ref name="West">{{cite journal|last1=Krieck|first1=Sven|last2=Görls|first2=Helmar|last3=Westerhausen|first3=Matthias|title=Mechanistic Elucidation of the Formation of the Inverse Ca(I) Sandwich Complex [(thf)3Ca(μ-C6H3-1,3,5-Ph3)Ca(thf)3] and Stability of Aryl-Substituted Phenylcalcium Complexes|journal=Journal of the American Chemical Society|volume=132|issue=35|pages=100818110534020|year=2010|pmid=20718434|doi=10.1021/ja105534w}}</ref>
|oxidation states comment=strongly [[base (chemistry)|basic]] oxide
|electronegativity=1.00
|number of ionization energies=4
|1st ionization energy=589.8
|2nd ionization energy=1145.4
|3rd ionization energy=4912.4
|atomic radius=[[1 E-10 m|197]]
|atomic radius calculated=
|covalent radius=[[1 E-10 m|176±10]]
|Van der Waals radius=[[1 E-10 m|231]]
|magnetic ordering=[[diamagnetism|diamagnetic]]
|electrical resistivity=
|electrical resistivity at 0=
|electrical resistivity at 20=33.6 n
|thermal conductivity=201
|thermal conductivity 2=
|thermal diffusivity=
|thermal expansion=
|thermal expansion at 25=22.3
|speed of sound=
|speed of sound rod at 20=3810
|speed of sound rod at r.t.=
|Young's modulus=20
|Shear modulus=7.4
|Bulk modulus=17
|Poisson ratio=0.31
|Mohs hardness=1.75
|Vickers hardness=
|Brinell hardness=167
|CAS number=7440-70-2
|isotopes=
{{Elementbox_isotopes_decay | mn=40 | sym=Ca | na=96.941% | hl=[[1 E19 s and more|>5.9×10<sup>21</sup> y]] | dm=[[double beta decay|β<sup>+</sup>β<sup>+</sup>]] | de=0.194 | pn=40 | ps=[[argon|Ar]] }}
{{Elementbox_isotopes_decay | mn=41 | sym=Ca | na=[[trace radioisotope|trace]] | hl=[[1 E12 s|1.03×10<sup>5</sup> y]] | dm=[[electron capture|ε]] | de=- | pn=41 | ps=[[potassium|K]] }}
{{Elementbox_isotopes_stable | mn=42 | sym=Ca | na=0.647% | n=22 }}
{{Elementbox_isotopes_stable | mn=43 | sym=Ca | na=0.135% | n=23 }}
{{Elementbox_isotopes_stable | mn=44 | sym=Ca | na=2.086% | n=24 }}
{{Elementbox_isotopes_decay | mn=45 | sym=Ca | na=[[synthetic radioisotope|syn]] | hl=[[1 E7 s|162.7 d]] | dm=[[beta decay|β<sup>−</sup>]] | de=0.258 | pn=45 | ps=[[Scandium|Sc]] }}
{{Elementbox_isotopes_decay | mn=46 | sym=Ca | na=0.004% | hl=[[1 E19 s and more|>2.8×10<sup>15</sup> y]] | dm=[[double beta decay|β<sup>−</sup>β<sup>−</sup>]] | de=0.988 | pn=46 | ps=[[titanium|Ti]] }}
{{Elementbox_isotopes_decay2 | mn=47 | sym=Ca | na=[[synthetic radioisotope|syn]] | hl=[[1 E5 s|4.536 d]] | dm1=[[beta decay|β<sup>−</sup>]] | de1=0.694, 1.99 | pn1=47 | ps1=[[Scandium|Sc]] |
dm2=[[gamma ray|γ]] | de2=1.297 | pn2= | ps2=- }}
{{Elementbox_isotopes_decay2 | mn=48 | sym=Ca | na=0.187% | hl=[[1 E19 s and more|4.3×10<sup>19</sup> y]] | dm1=[[double beta decay|β<sup>−</sup>β<sup>−</sup>]] | de1=4.274 | pn1=48 | ps1=[[titanium|Ti]] | dm2=[[beta decay|β<sup>−</sup>]]<br/>(not observed) | de2=0.0058 | pn2=48 | ps2=[[scandium|Sc]] }}
|isotopes comment=
|discovered by=[[Humphry Davy]]
|discovery date=1808
|first isolation by=Humphry Davy
|first isolation date=1808
}}
[[File:Calcium unter Argon Schutzgasatmosphäre.jpg|thumb|Very pure calcium metal, not corroded]]
[[File:Calcium.jpg|thumb|Calcium metal in air, corroded]]
'''Calcium''' is a [[chemical element]]. Its symbol on the [[periodic table]] (a list of all the elements) is '''Ca'''. Its [[atomic number]] is 20. (The atomic number says where Calcium sits in the periodic table.) It has 20 [[proton]]s and 20 [[electron]]s (if is an atom, see [[ion]]). The most common [[isotope]]s are Ca-40 and Ca-44. Its [[mass number]] is about 40.08.
Calcium is very important in the human body, It is required for minerals and bones.
==Properties==
===Physical properties===
Calcium is a soft white-gray [[metal]]. It is an [[alkaline earth metal]]. It melts at a quite high temperature for a reactive metal. It is a little harder than [[lead]]. It has two [[allotrope]]s. It does not conduct electricity as well as copper, but is much lighter in weight.
===Chemical properties===
[[File:Calcium air 2.theora.ogv|thumb|Calcium metal burning]]
It reacts with water to produce [[hydrogen]] and [[calcium hydroxide]]. It reacts with water very fast when it is powdered. When it is in a chunk, it starts reacting slowly because calcium hydroxide makes a coating that does not dissolve on the calcium. If a little [[acid]] is added to calcium hydroxide, it dissolves it, making the calcium react very fast. It burns when powdered to make a reddish flame. This makes [[calcium oxide]]. It also makes [[calcium nitride]] when heated. It can react with [[halogen]]s to make calcium halides like [[calcium chloride]] with [[chlorine]].
===Calcium compounds===
Calcium forms chemical compounds in the +2 [[oxidation state]]. Calcium compounds are colorless. Most calcium compounds are not toxic. They are needed in the human body, actually. They are unreactive as far as calcium ions go. Calcium oxide was used to make [[limelight]]s, which have a flame heating calcium oxide and makes it glow very bright.
*[[Calcium bromate]]
*[[Calcium carbonate]]
*[[Calcium chloride]]
*[[Calcium hydroxide]]
*[[Calcium nitrate]]
*[[Calcium nitride]]
*[[Calcium oxide]]
*[[Calcium permanganate]]
*[[Calcium phosphate]]
*[[Dicalcium phosphate]]
*[[Monocalcium phosphate]]
<gallery>
File:Calcium hydroxide.jpg|Calcium hydroxide
File:Calcium chloride.jpg|Calcium chloride
File:Calcium sulfate hemihydrate.jpg|Calcium sulfate hydrated (with water)
File:Dusičnan vápenatý.JPG|Calcium nitrate
</gallery>
==Occurrence==
===In the ground===
[[File:Calcite-cu01abg.jpg|thumb|Calcite]]
Calcium is not found as a metal in the ground; it is too reactive. [[Calcium carbonate]], also known as [[calcite]], is the most common calcium mineral.
=== Calcium in cells ===
It is important to know how cells work. Many cells have ''calcium channels'' on their surface. These are openings where calcium ions can enter the cell. The cell is told to act and it opens the channels. Once in the cell calcium ions activates many [[protein]]s to do specific things. For example, when it goes into [[muscle]] cells, it makes them ''contract'' (shorten so the muscle pulls.) When it goes into [[nerve]] cells, it triggers electrical impulses that send a messages. When it goes into [[white blood cell]]s it makes them fight germs.
Calcium ions are important to cells, but too many calcium ions can be bad. If a cell gets more calcium ion than it needs it can die. This is why the amount of calcium ion in cells is highly regulated. Conversely, not enough calcium ion is bad. Cells must have the right amount to function properly.
Sometimes cells are unhealthy and need to die in for the body to replace them with new, healthy cells. This keeps the whole [[organism]] healthy. Cells know when they should die and can trigger reactions to end their life cycles in many ways. When this happens it is called [[apoptosis]], also known as a 'programmed cell death' (''planned'' cell death.) One way cells accomplish ''apoptosis'' by taking in toxic levels of calcium ions.
Calcium is very important for the human body.
=== Calcium storage ===
[[Bone]]s contain most of the calcium ion in the human body. If we need more calcium for our [[blood]], [[muscles]], or other [[tissue (biological)|tissue]], it comes from the bones. If we have extra calcium it goes into bones.
Calcium as an element is not found in the human body, just calcium ions in the form of [[chemical compound]]s.
=== Calcium regulation ===
Organisms need to keep calcium ion levels very well controlled. High calcium levels are bad, and low calcium levels are bad.
The body controls this by changing
* how much calcium we get from the food we eat
* how much calcium we lose in [[urine]]
* how much calcium is put in bones
The control of calcium in the body is called ''calcium [[metabolism]]''.
The body controls calcium levels with many [[hormone]]s. Calcitonin, Parathyroid hormone ([[acronym]] PTH), and [[Vitamin D]] are the most important hormones in ''calcium metabolism''. (Vitamin D is a hormone but it is called a [[vitamin]].)
==Preparation==
Calcium metal is made by [[electrolysis]] of melted [[calcium chloride]]. It has to be very hot to melt it. The calcium metal is liquid.
==Uses==
===As an element===
Calcium is used in the [[reduction (chemistry)|reduction]] of other metals. It can also be used to make alloys with other metals.
===As chemical compounds===
[[File:Concrete pouring 0020.jpg|thumb|right|Concrete used to make a building]]
Calcium compounds are also important in [[chemistry]]. It is important for making things. It is a part of [[cement]] which is needed to make [[concrete]] (a hard substance that many buildings are made from.)
Calcium is part of [[calcium oxide]]. Calcium oxide is used to make [[paper]], [[pottery]], food, and to purify water (make it good to drink.) Calcium carbonate is used as a calcium supplement. Calcium permanganate can be used as a rocket [[wikt:propellant|propellant]].
==Safety==
Calcium is toxic as an element. It reacts with water and makes a strong [[base (chemistry)|base]], calcium hydroxide. Calcium compounds are not toxic unless the anion is toxic. Calcium permanganate is only toxic because of the [[permanganate]], not the calcium.
==Related pages==
*[[Calcium compounds]]
==Sources==
{{Reflist}}
{{Periodic Table}}
[[Category:Alkaline earth metals]]
|name=calcium
|pronounce={{IPAc-en|ˈ|k|æ|l|s|i|ə|m}} {{respell|KAL|see-əm}}
|number=20
|symbol=Ca
|left=[[potassium]]
|right=[[scandium]]
|above=[[magnesium|Mg]]
|below=[[strontium|Sr]]
|series=alkaline earth metal
|series comment=
|group=2
|period=4
|block=s
|series color=
|phase color=
|appearance=dull gray, silver
|image name=Calcium unter Argon Schutzgasatmosphäre.jpg
|image size=
|image name comment=
|image name 2=Calcium Spectrum.png
|image name 2 comment=Spectral lines of calcium
|atomic mass=40.078
|atomic mass 2=4
|atomic mass comment=
|electron configuration=[[[argon|Ar]]] 4s<sup>2</sup>
|electrons per shell=2, 8, 8, 2
|color=
|phase=solid
|phase comment=
|density gplstp=
|density gpcm3nrt=1.55
|density gpcm3nrt 2=
|density gpcm3mp=1.378
|melting point K=1115
|melting point C=842
|melting point F=1548
|boiling point K=1757
|boiling point C=1484
|boiling point F=2703
|triple point K=
|triple point kPa=
|critical point K=
|critical point MPa=
|heat fusion=8.54
|heat fusion 2=
|heat vaporization=154.7
|heat capacity=25.929
|vapor pressure 1=864
|vapor pressure 10=956
|vapor pressure 100=1071
|vapor pressure 1 k=1227
|vapor pressure 10 k=1443
|vapor pressure 100 k=1755
|vapor pressure comment=
|crystal structure=face-centered cubic
|oxidation states='''+2''', +1<ref name="West">{{cite journal|last1=Krieck|first1=Sven|last2=Görls|first2=Helmar|last3=Westerhausen|first3=Matthias|title=Mechanistic Elucidation of the Formation of the Inverse Ca(I) Sandwich Complex [(thf)3Ca(μ-C6H3-1,3,5-Ph3)Ca(thf)3] and Stability of Aryl-Substituted Phenylcalcium Complexes|journal=Journal of the American Chemical Society|volume=132|issue=35|pages=100818110534020|year=2010|pmid=20718434|doi=10.1021/ja105534w}}</ref>
|oxidation states comment=strongly [[base (chemistry)|basic]] oxide
|electronegativity=1.00
|number of ionization energies=4
|1st ionization energy=589.8
|2nd ionization energy=1145.4
|3rd ionization energy=4912.4
|atomic radius=[[1 E-10 m|197]]
|atomic radius calculated=
|covalent radius=[[1 E-10 m|176±10]]
|Van der Waals radius=[[1 E-10 m|231]]
|magnetic ordering=[[diamagnetism|diamagnetic]]
|electrical resistivity=
|electrical resistivity at 0=
|electrical resistivity at 20=33.6 n
|thermal conductivity=201
|thermal conductivity 2=
|thermal diffusivity=
|thermal expansion=
|thermal expansion at 25=22.3
|speed of sound=
|speed of sound rod at 20=3810
|speed of sound rod at r.t.=
|Young's modulus=20
|Shear modulus=7.4
|Bulk modulus=17
|Poisson ratio=0.31
|Mohs hardness=1.75
|Vickers hardness=
|Brinell hardness=167
|CAS number=7440-70-2
|isotopes=
{{Elementbox_isotopes_decay | mn=40 | sym=Ca | na=96.941% | hl=[[1 E19 s and more|>5.9×10<sup>21</sup> y]] | dm=[[double beta decay|β<sup>+</sup>β<sup>+</sup>]] | de=0.194 | pn=40 | ps=[[argon|Ar]] }}
{{Elementbox_isotopes_decay | mn=41 | sym=Ca | na=[[trace radioisotope|trace]] | hl=[[1 E12 s|1.03×10<sup>5</sup> y]] | dm=[[electron capture|ε]] | de=- | pn=41 | ps=[[potassium|K]] }}
{{Elementbox_isotopes_stable | mn=42 | sym=Ca | na=0.647% | n=22 }}
{{Elementbox_isotopes_stable | mn=43 | sym=Ca | na=0.135% | n=23 }}
{{Elementbox_isotopes_stable | mn=44 | sym=Ca | na=2.086% | n=24 }}
{{Elementbox_isotopes_decay | mn=45 | sym=Ca | na=[[synthetic radioisotope|syn]] | hl=[[1 E7 s|162.7 d]] | dm=[[beta decay|β<sup>−</sup>]] | de=0.258 | pn=45 | ps=[[Scandium|Sc]] }}
{{Elementbox_isotopes_decay | mn=46 | sym=Ca | na=0.004% | hl=[[1 E19 s and more|>2.8×10<sup>15</sup> y]] | dm=[[double beta decay|β<sup>−</sup>β<sup>−</sup>]] | de=0.988 | pn=46 | ps=[[titanium|Ti]] }}
{{Elementbox_isotopes_decay2 | mn=47 | sym=Ca | na=[[synthetic radioisotope|syn]] | hl=[[1 E5 s|4.536 d]] | dm1=[[beta decay|β<sup>−</sup>]] | de1=0.694, 1.99 | pn1=47 | ps1=[[Scandium|Sc]] |
dm2=[[gamma ray|γ]] | de2=1.297 | pn2= | ps2=- }}
{{Elementbox_isotopes_decay2 | mn=48 | sym=Ca | na=0.187% | hl=[[1 E19 s and more|4.3×10<sup>19</sup> y]] | dm1=[[double beta decay|β<sup>−</sup>β<sup>−</sup>]] | de1=4.274 | pn1=48 | ps1=[[titanium|Ti]] | dm2=[[beta decay|β<sup>−</sup>]]<br/>(not observed) | de2=0.0058 | pn2=48 | ps2=[[scandium|Sc]] }}
|isotopes comment=
|discovered by=[[Humphry Davy]]
|discovery date=1808
|first isolation by=Humphry Davy
|first isolation date=1808
}}
[[File:Calcium unter Argon Schutzgasatmosphäre.jpg|thumb|Very pure calcium metal, not corroded]]
[[File:Calcium.jpg|thumb|Calcium metal in air, corroded]]
'''Calcium''' is a [[chemical element]]. Its symbol on the [[periodic table]] (a list of all the elements) is '''Ca'''. Its [[atomic number]] is 20. (The atomic number says where Calcium sits in the periodic table.) It has 20 [[proton]]s and 20 [[electron]]s (if is an atom, see [[ion]]). The most common [[isotope]]s are Ca-40 and Ca-44. Its [[mass number]] is about 40.08.
Calcium is very important in the human body, It is required for minerals and bones.
==Properties==
===Physical properties===
Calcium is a soft white-gray [[metal]]. It is an [[alkaline earth metal]]. It melts at a quite high temperature for a reactive metal. It is a little harder than [[lead]]. It has two [[allotrope]]s. It does not conduct electricity as well as copper, but is much lighter in weight.
===Chemical properties===
[[File:Calcium air 2.theora.ogv|thumb|Calcium metal burning]]
It reacts with water to produce [[hydrogen]] and [[calcium hydroxide]]. It reacts with water very fast when it is powdered. When it is in a chunk, it starts reacting slowly because calcium hydroxide makes a coating that does not dissolve on the calcium. If a little [[acid]] is added to calcium hydroxide, it dissolves it, making the calcium react very fast. It burns when powdered to make a reddish flame. This makes [[calcium oxide]]. It also makes [[calcium nitride]] when heated. It can react with [[halogen]]s to make calcium halides like [[calcium chloride]] with [[chlorine]].
===Calcium compounds===
Calcium forms chemical compounds in the +2 [[oxidation state]]. Calcium compounds are colorless. Most calcium compounds are not toxic. They are needed in the human body, actually. They are unreactive as far as calcium ions go. Calcium oxide was used to make [[limelight]]s, which have a flame heating calcium oxide and makes it glow very bright.
*[[Calcium bromate]]
*[[Calcium carbonate]]
*[[Calcium chloride]]
*[[Calcium hydroxide]]
*[[Calcium nitrate]]
*[[Calcium nitride]]
*[[Calcium oxide]]
*[[Calcium permanganate]]
*[[Calcium phosphate]]
*[[Dicalcium phosphate]]
*[[Monocalcium phosphate]]
<gallery>
File:Calcium hydroxide.jpg|Calcium hydroxide
File:Calcium chloride.jpg|Calcium chloride
File:Calcium sulfate hemihydrate.jpg|Calcium sulfate hydrated (with water)
File:Dusičnan vápenatý.JPG|Calcium nitrate
</gallery>
==Occurrence==
===In the ground===
[[File:Calcite-cu01abg.jpg|thumb|Calcite]]
Calcium is not found as a metal in the ground; it is too reactive. [[Calcium carbonate]], also known as [[calcite]], is the most common calcium mineral.
=== Calcium in cells ===
It is important to know how cells work. Many cells have ''calcium channels'' on their surface. These are openings where calcium ions can enter the cell. The cell is told to act and it opens the channels. Once in the cell calcium ions activates many [[protein]]s to do specific things. For example, when it goes into [[muscle]] cells, it makes them ''contract'' (shorten so the muscle pulls.) When it goes into [[nerve]] cells, it triggers electrical impulses that send a messages. When it goes into [[white blood cell]]s it makes them fight germs.
Calcium ions are important to cells, but too many calcium ions can be bad. If a cell gets more calcium ion than it needs it can die. This is why the amount of calcium ion in cells is highly regulated. Conversely, not enough calcium ion is bad. Cells must have the right amount to function properly.
Sometimes cells are unhealthy and need to die in for the body to replace them with new, healthy cells. This keeps the whole [[organism]] healthy. Cells know when they should die and can trigger reactions to end their life cycles in many ways. When this happens it is called [[apoptosis]], also known as a 'programmed cell death' (''planned'' cell death.) One way cells accomplish ''apoptosis'' by taking in toxic levels of calcium ions.
Calcium is very important for the human body.
=== Calcium storage ===
[[Bone]]s contain most of the calcium ion in the human body. If we need more calcium for our [[blood]], [[muscles]], or other [[tissue (biological)|tissue]], it comes from the bones. If we have extra calcium it goes into bones.
Calcium as an element is not found in the human body, just calcium ions in the form of [[chemical compound]]s.
=== Calcium regulation ===
Organisms need to keep calcium ion levels very well controlled. High calcium levels are bad, and low calcium levels are bad.
The body controls this by changing
* how much calcium we get from the food we eat
* how much calcium we lose in [[urine]]
* how much calcium is put in bones
The control of calcium in the body is called ''calcium [[metabolism]]''.
The body controls calcium levels with many [[hormone]]s. Calcitonin, Parathyroid hormone ([[acronym]] PTH), and [[Vitamin D]] are the most important hormones in ''calcium metabolism''. (Vitamin D is a hormone but it is called a [[vitamin]].)
==Preparation==
Calcium metal is made by [[electrolysis]] of melted [[calcium chloride]]. It has to be very hot to melt it. The calcium metal is liquid.
==Uses==
===As an element===
Calcium is used in the [[reduction (chemistry)|reduction]] of other metals. It can also be used to make alloys with other metals.
===As chemical compounds===
[[File:Concrete pouring 0020.jpg|thumb|right|Concrete used to make a building]]
Calcium compounds are also important in [[chemistry]]. It is important for making things. It is a part of [[cement]] which is needed to make [[concrete]] (a hard substance that many buildings are made from.)
Calcium is part of [[calcium oxide]]. Calcium oxide is used to make [[paper]], [[pottery]], food, and to purify water (make it good to drink.) Calcium carbonate is used as a calcium supplement. Calcium permanganate can be used as a rocket [[wikt:propellant|propellant]].
==Safety==
Calcium is toxic as an element. It reacts with water and makes a strong [[base (chemistry)|base]], calcium hydroxide. Calcium compounds are not toxic unless the anion is toxic. Calcium permanganate is only toxic because of the [[permanganate]], not the calcium.
==Related pages==
*[[Calcium compounds]]
==Sources==
{{Reflist}}
{{Periodic Table}}
[[Category:Alkaline earth metals]]