Antimony Facts – Symbol, Definition, Uses

Antimony Facts

Antimony is a metalloid with the chemical symbol Sb and atomic number 51. It is a brittle solid with a metallic luster. Antimony occurs in native form in the Earth’s crust, so people have used it for thousands of years. In modern times, you encounter it as a flame retardant in clothing and as a catalyst in PET plastic bottles.


The use of antimony dates back to ancient civilizations. The early Egyptians and Greeks used its compounds for cosmetics and medicines as early as 3100 BC. An antimony vase from Chaldea (present day Iraq) dates back to around 3000 BC. German metallurgist Andreas Libavius first isolated pure antimony as an element in 1615.

Antimony Name

The element with atomic number 51 has had many names, including stm, stimmi, ithmid, and stibium. The name antimonium appears in Arabic medical treatises from 1050-1100. The origin of the name “antimony” is uncertain. Some researchers believe it comes from the Greek word “antimonos,” meaning “not alone,” reflecting its common presence in compounds rather than in pure form. Another etymology suggests the name comes from the French antimoine, meaning “monk-killer”. Early alchemists were often monks and may have met sickness or an untimely end from working with antimony or its compounds.

Antimony Symbol

Antimony is one of the elements that has a symbol (Sb) that does not match its modern name. The symbol comes from the Latin name for the element, stibium. Jöns Jakob Berzelius assigned the symbol based on the earlier element name.

Appearance and Allotropes

The most stable and common allotrope is metallic antimony, which appears as a shiny, silvery-white, brittle solid. A less common allotrope is amorphous black antimony. While there are reports of yellow antimony and an explosive form, these structures likely contain impurities and are not true allotropes.

Element Group

Antimony is a metalloid or semimetal and is part of Group 15 of the periodic table, also known as the nitrogen group or pnictogens. Other elements in this group include nitrogen, phosphorus, arsenic, and bismuth. Overall, these elements are good semiconductors and form amphoteric oxides.


Natural antimony is a mix of two stable isotopes. 121Sb constitutes about 57.36% of natural antimony. 123Sb makes about 42.64% of natural antimony.

There are 35 synthetic radioisotopes, with 125Sb and 124Sb being the most notable due to their use in various applications, including medical diagnostics and research. Antimony is the lightest element with an alpha decay branch for its isotopes.

Abundance and Sources

Antimony occurs as a pure element in nature, but primarily exists in compounds. Its main source is the mineral stibnite (Sb2S3). It is also found in smaller quantities in other minerals such as valentinite and senarmontite.

The element’s abundance in the Earth’s crust is approximately 0.2-0.5 ppm. The abundance in the ocean is around 0.2-0.3 ppb. The human body naturally contains trace amounts of antimony.

China produces around 74% of the world’s supply of the element. Other producers are Tajikistan and Russia.


Antimony is typically extracted from stibnite ore through a process involving roasting, which converts the ore into antimony oxide (Sb2O3). Reducing this oxide with carbon or iron yields metallic antimony.


Antimony has a wide range of applications. Around 48% finds use in flame retardants, 33% in lead-acid batteries, and 8% in plastics.

  • Flame Retardants: Antimony trioxide (Sb2O3) is a critical component in flame-retardant formulations. Combined with halogens, it enhances the fire resistance of materials by promoting the formation of a char layer that acts as a barrier to flames. These chemicals are common in fabrics, plastics, and building materials.
  • Catalysts: Antimony trioxide is a catalyst in the polymerization of polyethylene terephthalate (PET), which finds wide use in plastic bottles. The compound is a catalysts for other polymers and various organic synthesis reactions.
  • Alloys: Antimony improves the hardness and strength of lead and tin alloys, commonly used in batteries, bullets, and bearings. Tin-antimony alloy occurs in pewter and in solder, because of its low melting point and strong bonds.
  • Semiconductors: Antimony is important in the electronics industry for making diodes, Hall-effect sensors, and infrared detectors.
  • Cosmetics: Kohl for eye cosmetics has used stibnite (Sb2S3) since Ancient Egyptian times, although the compound has largely been replaced.
  • Medicine: Antimony compounds are effective against leishmaniasis and schistosomiasis. For the most part, the toxicity of the compounds limits modern usefulness. However, they still have applications as an antiprotozoal medication and in veterinary medicine.
  • Glass and Ceramics: Antimony oxide improves the clarity and quality of glass and ceramics.
  • Pigments: Lead antimonate is a bright yellow pigment for paints, ceramics, and plastics.

Oxidation States

Electron Levels of an Antimony Atom

Antimony exhibits oxidation states ranging from -3 to +5. The +3 and +5 states are the most common in its compounds.

Biological Role and Toxicity

Antimony does not have a known essential biological role in humans or other organisms.

The element and its compounds are toxic to humans and other animals. Antimony accumulates in the environment, causing an environmental impact.

Antimony poisoning is similar to arsenic poisoning, mainly resulting in myocarditis and other effects from cardiotoxicity. It can be fatal. Acute exposure causes skin irritation, respiratory issues, and gastrointestinal symptoms. Prolonged exposure leads to more severe health problems and damages the lungs, heart, liver, and kidneys.

Antimony leaches out of PET bottles into water and even more into acidic liquids, like juice. Low levels of antimony in saliva are linked to tooth decay.

Table of Key Antimony Facts

Atomic Number51
Atomic Weight121.760
Electron Configuration[Kr] 4d10 5s2 5p3
Electrons per Shell2, 8, 18, 18, 5
State of MatterSolid
Melting Point630.63°C
Boiling Point15635°C
Density6.694 g/cm³
Heat of Fusion19.79 kJ/mol
Heat of Vaporization193.43 kJ/mol
Molar Heat Capacity25.23 J/(mol·K)
Oxidation States-3, -2, -1, 0, +1, +2, +3, +4, +5
Ionization Energies (1st, 2nd, 3rd)834, 1594.9, 2440 kJ/mol
Atomic Radius140 pm
Covalent Radius139 pm
Crystal StructureRhombohedral
Thermal Conductivity24.4 W/(m·K)
Electrical Resistivity417 nΩ·m
Magnetic OrderingDiamagnetic
Young’s Modulus55 GPa
Shear Modulus20 GPa
Mohs Hardness3.0


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