Antimony (Sb)

Stable isotopes of antimony available from ISOFLEX

Isotope Z(p) N(n) Atomic Mass Natural Abundance Enrichment Level Chemical Form
Sb-121 51 60 120.903822 57.30% >99.00% Metal
Sb-121 51 60 120.903822 57.30% >99.00% Oxide
Sb-123 51 62 122.904215 42.70% >98.00%  Metal 
Sb-123 51 62 122.904215 42.70% 94.00-98.00% Oxide

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Antimony was recognized in compounds by the ancients and was known as a metal at the beginning of the 17th century, possibly much earlier. Its name derives from the Greek words anti + monos, meaning “not alone,” and its symbol, Sb, comes from the Latin word stibium (“antimony”). Its most important mineral is stibnite, which formed the basis of black eye makeup in biblical times.

The French chemist Nicolas Lémery conducted early studies on antimony chemistry. It is a silvery-white, brittle, metallic element with a crystal system-hexagonal structure. It exists in two unstable allotropic forms – a yellow modification and a dark-gray lustrous amorphous powder – both of which revert to crystalline form.

Antimony is stable in dry air, not readily attacked by moisture, but slowly oxidizes in moist air. Oxidation may result under controlled conditions, forming tri-, tetra- and pentaoxides. Antimony reacts with sulfur, combining in all proportions, forming tri- and pentasulfides. It is oxidized by nitric acid, forming a gelatinous precipitate of hydrated antimony pentoxide. It does not react with cold dilute sulfuric acid; however, reaction occurs in hot concentrated acid: an oxysulfate of indefinite composition and low acid-solubility is formed. It reacts with hydrofluoric acid to form soluble antimony trifluoride and pentafluoride.

Antimony alloys have many commercial applications. The metal makes its alloys hard and stiff and imparts resistance to corrosion; such alloys are used in battery grids and parts, tank linings, pipes and pumps. The lead plates in lead storage batteries comprise 94% lead and 6% antimony. Babbit metal — an alloy of antimony, tin, and copper — is used to make antifriction machine bearings. Alloys made from very high-purity-grade antimony with indium, gallium and bismuth, are used as infrared detectors, diodes, Hall effect devices and thermoelectric coolers.

Properties of Antimony

Name Antimony
Symbol Sb
Atomic number 51
Atomic weight 121.75
Standard state Solid at 298 °K
CAS Registry ID 7440-36-0
Group in periodic table 15
Group name Pnictogen
Period in periodic table 5
Block in periodic table p-block
Color Silvery lustrous gray
Classification Semi-metallic
Melting point 630.5 °C
Boiling point 1635 °C
Thermal conductivity 24 W/(m·K)
Electrical resistivity 40 μΩ·cm
Electronegativity 1.82
Specific heat 207 J/(kg·K)
Heat of vaporization 195.2 kJ·mol-1
Heat of fusion 200 kJ·mol-1
Density of liquid 6.53 g/cm3 at 630.5 °C
Density of solid 6.697 g/cm3
Electronic configuration [Kr]4d105s25p3
Atomic radius 1.41 Å
Covalent radius Sb3+: 1.21 Å
Oxidation states -3, 0, +3, +5


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