Difference between revisions of "Antimony"

Revision as of 11:25, 22 February 2016

Antimony,  ₅₁Sb

Antimony lump.
General properties
Name, symbol	Antimony, Sb
Alternative name	Stibium
Allotropes	Metallic, explosive, black, yellow
Appearance	Silvery lustrous gray
Antimony in the periodic table
As ↑ Sb ↓ Bi Tin ← Antimony → Tellurium
Atomic number	51
Standard atomic weight (Ar)	121.760
Group, block	, p-block
Period	period 5
Electron configuration	[Kr] 4d10 5s2 5p3
per shell	2, 8, 18, 18, 5
Physical properties
Silvery-gray
Phase	Solid
Melting point	903.78 K ​(630.63 °C, ​1167.13 °F)
Boiling point	1908 K ​(1635 °C, ​2975 °F)
Density near r.t.	6.697 g/cm3
when liquid, at	6.53 g/cm3
Heat of fusion	19.79 kJ/mol
Heat of	193.43 kJ/mol
Molar heat capacity	25.23 J/(mol·K)
pressure
Atomic properties
Oxidation states	5, 4, 3, 2, 1, −1, −2, −3 ​(an amphoteric oxide)
Electronegativity	Pauling scale: 2.05
energies	1st: 834 kJ/mol 2nd: 1594.9 kJ/mol 3rd: 2440 kJ/mol (more)
Atomic radius	empirical: 140 pm
Covalent radius	139±5 pm
Miscellanea
Crystal structure	​
Speed of sound thin rod	3420 m/s (at 20 °C)
Thermal expansion	11 µm/(m·K)
Thermal conductivity	24.4 W/(m·K)
Electrical resistivity	417 nΩ·m (at 20 °C)
Magnetic ordering	Diamagnetic
Young's modulus	55 GPa
Shear modulus	20 GPa
Bulk modulus	42 GPa
Mohs hardness	3.0
Brinell hardness	294–384 MPa
CAS Registry Number	7440-36-0
History
Discovery	3000 BC
First isolation	Vannoccio Biringuccio (1540)
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Antimony is a chemical element with symbol Sb (from Latin: stibium, though in many countries it's called stibium) and atomic number 51. It is a metalloid.

Properties

Chemical

Antimony is stable in air at room temperature, but will burn in air to give antimony(III) oxide:

4 Sb + 3 O₂ → 2 Sb₂O₃

Antimony pentoxide (Sb₄O₁₀) cannot form by burning the element in open air, and is obtained by oxidizing antimony with concentrated nitric acid. Antimony also forms a mixed-valence oxide, antimony tetroxide (Sb₂O₄), which features both Sb(III) and Sb(V). Unlike the oxides of phosphorus and arsenic, antimony oxides are amphoteric, and do not form well-defined oxoacids and react with acids to form antimony salts.

Antimony is resistant to attack by most acids.

Antimony forms two series of halides: SbX₃ and SbX₅.

The trihalides are formed by reacting antimony, antimony(III) oxide or antimony(III) sulfide with hydrohalic acids, in inert conditions. The presence of moisture leads to hydrolysis. The pentahalides are formed by oxidizing the trihalides with their respective halogen.

Organoantimony compounds are typically prepared by alkylation of antimony halides with Grignard reagents, in an aprotic solvent. A large variety of compounds are known with both Sb(III) and Sb(V) centers, including mixed halo-organic derivatives, anions, and cations. Examples include triphenylstibine Sb(C₆H₅)₃, chlorodiphenylstibine Sb(C₆H₅)₂Cl, etc. Pentacoordinated organoantimony compounds are common, examples being Sb(C₆H₅)₅ and several related halides.

Physical

Antimony is a silvery gray metalloid. It has several allotrope forms:

• Metallic: The most stable form of antimony. It has the aspect of a brittle, silver-white solid. It melts at 630.63 °C and boils at 1635 °C. It has a density of 6.697 g/cm³.
• Black: Formed upon rapid cooling of metallic antimony vapors. It has the same crystal structure as red phosphorus and black arsenic, but is much more reactive. It oxidizes in air and may ignite spontaneously. At 100 °C, black antimony gradually transforms into the stable metallic form.
• Explosive: can be made via electrolysis of antimony(III) chloride. If scratched with a sharp object, an exothermic reaction occurs and white fumes are given off as metallic antimony is formed. Can detonate if grounded with a pestle in a mortar.
• Yellow: The most unstable allotrope form. Can only be made by oxidation of stibine (SbH₃) at −90 °C. Above this temperature and in ambient light, this metastable allotrope transforms into the more stable black allotrope.

Availability

Antimony is sold by various chemical suppliers and can also be found on eBay.

It can also be found in certain solders, as an alloy with tin.

Free antimony occurs in a few mines around the world.

Isolation

Antimony can be extracted by reducing it's ore, stibnite (Sb₂S₃) with a reducing agent, such as iron. Carbon can also be used.

Projects

• Make antimony halides
• Make antimony alloys
• Make explosive antimony

Handling

Safety

Antimony does not affect human and environmental health significantly. Inhalation of antimony trioxide (and similar poorly soluble Sb(III) dust particles such as antimony dust) is however considered harmful and suspected of causing cancer. Prolonged skin contact with antimony dust may cause dermatitis. Certain organometallic compounds of antimony may cause blisters on contact with unprotected skin.

Storage

Antimony should be stored in closed bottles, away from corrosive chemicals.

Disposal

Antimony is best recycled. Antimony compounds should be reduced to antimony element or oxide and either recycled or taken to disposal centers.

References

Sciencemadness library

• Antimony : its history, chemistry, mineralogy

Relevant Sciencemadness threads

• Remarkable reaction of antimony
• Making Antimony Metal