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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


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
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)
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
Atomic radius empirical: 140 pm
Covalent radius 139±5 pm
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
Discovery 3000 BC
First isolation Vannoccio Biringuccio (1540)
· references

Antimony is a chemical element with symbol Sb (from Latin: stibium, though in some countries it's called stibium or a variation of the word) and atomic number 51. It is a metalloid.



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.


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.


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

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

Free antimony occurs in a few mines around the world.


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


  • Make antimony halides
  • Make antimony alloys
  • Make explosive antimony
  • Element collecting



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.


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


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


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