Calcium

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Other names/abbreviations:

Ca

Element no:	20
Element group:	2 (IUPAC) II A (American labelling) II A (European labelling) Alkaline earth metals
Element type:	Metals
CAS-Number:	7440-70-2
EINECS-Number:	231-179-5

Chemical properties

Reaction of calcium with acids
Calcium metal dissolves readily in dilute or concentrated hydrochloric acid forming Ca(II) ions and hydrogen gas, H₂.

Ca (s) + 2 HCl (aq) Ca²⁺ (aq) + 2 Cl^- (aq) + H₂ (g)


Reaction of calcium with air
At room temperature, calcium reacts with oxygen, forming a thin layer of CaO, that protects the metal from further oxidation. Calcium can be ignited and will when burning react with both oxygen and nitrogen forming calcium oxide, CaO, and calcium nitride, Ca₃N₂.

2 Ca (s) + O₂ (g) 2 CaO (s)
3 Ca (s) + N₂ (g) Ca₃N₂ (s)


Reaction of calcium with carbonate ions
Calcium ions are precipitated by carbonate ions in neutral to alkaline solutions.

Ca²⁺ (aq) + CO₃^2- (aq) CaCO₃ (s) [white]


Reaction of calcium with halogens
Calcium reacts readily halogens forming the corresponding dihalides. The reactions with fluorine and chlorine are exothermic while the reactions with bromine and iodine are endothermic.

Ca (s) + F₂ (g) CaF₂ (s)
Ca (s) + Cl₂ (g) CaCl₂ (s)
Ca (s) + Br₂ (g) CaBr₂ (s)
Ca (s) + I₂ (g) CaI₂ (s)


Reaction of calcium with hydroxide
Calcium ions can be precipitated by strong bases provided the concentration of calcium is sufficient.

Ca²⁺ (aq) + 2 OH^- (aq) Ca(OH)₂ (s)


Reaction of calcium with oxalate
Calcium ions are precipitated by oxalate ions.

Ca²⁺ (aq) + HC₂O₄^- (aq) CaC₂O₄ (s) [white] + H⁺ (aq)

The oxalate can be dissolved by mineral acids but not acetic acid.


Reaction of calcium with phosphate
Calcium ions are precipitated by phosphate ions in alkaline solutions.

5 Ca²⁺ (aq) + 3 PO₄^3- (aq) + OH^- (aq) Ca₅(SO₄)₃OH (s) [white]


Reaction of calcium with sulfate
Calcium ions are precipitated by sulfate ions in neutral to alkaline solutions.

Ca²⁺ (aq) + SO₄^2- (aq) CaSO₄ (s) [white]


Reaction of calcium with sulfide
Calcium ions can not be precipitated by sulfide.


Reaction of calcium with water
Calcium reacts slowly with water, forming calcium hydroxide and hydrogen.

Ca (s) + 2 H₂O (l) Ca(OH)₂ (aq) + H₂ (g)


Solubility
Water: 4 g/L (Approximately, 20 °C) [4]

Quantitative analysis

Method 3500-Ca C Inductively Coupled Plasma Method [1]. A portion of the sample is digested in a combination of acids. The digest is aspirated into an 8,000 K argon plasma where resulting light emission is quantified for 30 elements simultaneously.

Method limit of detection in water = 0.10 mg/L
Method limit of detection in soil = 100.0 mg/kg

Safety

Symbol: F
R-phrases: 15
S-phrases: 8-24/25-43

Physical properties

Appearance
	Physical state @ 20°C:	Solid
	Color:	Metallic sheen [4]
	Odor:	Odourless [4]

Bulk properties
	Molecular weight (g/mol):	40.078(4) [2]
	Melting point (°C):	842 [2]
	Boiling point (°C):	1494 [2]
	Density (g/cm3):	1.55 [2]
	Molar volume (cm3):	25.86 (20 °C) [3]
	Velocity of sound (m/s):	3810
	Elastic properties: Young's modulus (GPa): Rigidity modulus (GPa): Bulk modulus (GPa): Poisson ratio:	20-28 [3] 7.9 [3] 17.2 [3] 0.31 [3]
	Hardness: Mineral hardness: Brinell hardness (MN/m2):	1.75 167

Thermodynamic properties
	ΔfH°gas (kJ/mol):	178 (Monoatomic) [2]
	ΔH°fusion (kJ/mol):	8.6 [2]
	ΔH°vaporization (kJ/mol):	155 [2]

Crystal structure
	Crystal type	Face centered cubic [3]

Electronic properties
	Electron configuration:	1s2-2s2-2p6-3s2-3p6-4s2
	Ionic radius (Å):	1.00 [2]

Conductivity
	e°(V):	-2.84 [2]
	Electrical resisitvity (μΩ·cm):	3.70 (20 °C) [3] 3.45 (25 °C) [3]

History

Origin of name:
From Latin "calx" meaning lime [5].

References

1: Standard Methods for the Analysis of Water and Wastewater, APHA, 1992, 18th edition

2: Greenwood,N.N., Earnshaw,A. Chemistry of the elements
2nd edition (1997) Edited by Greenwood,N.N., Earnshaw,A. pp. 1-1340, Butterworth-Heinemann. Oxford. Great Britain

3: Buch,A. Pure Metals Properties. A Scientific-Technical Handbook
1st edition (1999) Edited by Buch,A. pp. 1-306, ASM International and Freund Publishing House Ltd. Ohio. USA

4: Merck. ChemDAT The Merck Chemical Database Ver. 1.1.5

5: CRC Handbook of Chemistry and Physics
75th edition (1994) Edited by Lide,D.R. , CRC Press Inc. Boca Raton, USA

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© Michael Pilgaard
Created: November 13, 2006
Last update: October 31, 2008