Strontium

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Other names/abbreviations:

Sr

Element no:	38
Element group:	2 (IUPAC) II A (American labelling) II A (European labelling) Alkaline earth metals
Element type:	Metals
CAS-Number:	7440-24-6
EINECS-Number:	231-133-4

Chemical properties

Reaction of strontium with hydroxide ions
Sr(II) is not precipitated by OH^- (S[Sr(OH)₂] = 0.8 g/100 ml @ 20 °C)


Reaction of strontium with carbonate
Sr(II) is precipitated by carbonate ions.

Sr²⁺ (aq) + CO₃^2- (aq) SrCO₃ (s)

The carbonate is a white crystalline precipitate that easily dissolves in acid

SrCO₃ (s) + NH₄⁺ (aq) Sr²⁺ (aq) + HCO₃^- (aq) + NH₃ (aq)


Reaction of strontium with chromate
Sr(II) is not precipitated by chromate ions in acetic acid.


Reaction of strontium with oxalate
Sr(II) is precipitated by ammonium oxalate

Sr²⁺ (aq) + C₂O₄^2- (aq) SrC₂O₄ (s)

The oxalate is a white crystalline precipitate that dissolves in mineral acids

SrC₂O₄ (s) + 2 H⁺ (aq) Sr²⁺ (aq) + H₂C₂O₄ (aq)


Reaction of strontium with sulfate
Sr(II) is precipitated by sulfate ions at neutral or slightly acidic solutions. The sulfate is a white crystalline precipitate.

Sr²⁺ + SO₄^2- SrSO₄ (s)

In strong acidic solutions SrSO₄ dissolves as the sulfate concentration becomes to small:

SO₄^2- + H⁺ HSO₄^-, L[SrSO₄] = 4·10^-7 M²


Reaction of strontium with sulfide
Sr(II) does not precipitated by H₂S or sulfide ions in acidic or alkaline solutions.


Solubility
Water: Reaction (20 °C) [4]

Quantitative analysis

Method 3500-Sr C Inductively Coupled Plasma Method [2]. 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 = 0.002 mg/L
Method limit of detection in soil = 1.00 mg/kg

Safety

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

Physical properties

Appearance
	Physical state @ 20°C:	Solid [4]
	Color:	Silver gray [4]
	Odor:	Odourless [4]

Bulk properties
	Molecular weight (g/mol):	87.62(1) [1]
	Melting point (°C):	769 [1]
	Boiling point (°C):	1382 [1]
	Density (g/cm3):	2.54 (20 °C) [4]
	Molar volume (cm3):	33.70 (20 °C) [3]
	Elastic properties: Young's modulus (GPa): Rigidity modulus (GPa): Bulk modulus (GPa):	15.7 [3] 6.03 [3] 12.0 [3]
	Hardnesses: Mineral hardness:	1.5 [2]

Thermodynamic properties
	ΔfH°gas (kJ/mol):	164 (monoatomic) [1]
	ΔfH°solid (kJ/mol):	0.0 [5]
	ΔH°fusion (kJ/mol):	8.2 [1] 7.43 [5]
	ΔH°vaporization (kJ/mol):	158 [1]
	S°gas (J/K·mol):	164.6 [5]
	S°solid (J/K·mol):	52.3 [5]
	ΔfG°gas (kJ/mol):	130.9 [5]
	Cp (gas) (J/K·mol):	20.8 (25 °C) [5]
	Cp (solid) (J/K·mol):	26.4 (25 °C) [5]
	Coeff. of linear thermal expansion (106 K-1):	22.5 (25 °C) [5]

Crystal structure
	Crystal type:	Face centered cubic [3]

Electronic properties
	Electron configuration:	1s2-2s2-2p6-3s2-3p6-3d10-4s2-4p6-5s2
	Ionic radius (Å):	1.18 [1]

Conductivity
	e°(V):	-2.89 [1]
	Electrical resisitvity (μΩ·cm):	13.50 (20 °C) [3] 13.50 (25 °C) [3]
	Thermal (W/m·K):	35.3 (27 °C) [5]

References

1: 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

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

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: October 6, 2008
Last update: October 14, 2008