Antimony – facts and properties

Position in the periodic table

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Occurrence and extraction

Antimony is rare in the Earth's crust. The most important ore is stibnite, also called antimony glance, a sulfide with the formula Sb₂S₃. Its shiny, needle-shaped crystals gave it the German name Spießglanz, meaning spear glance. China is the largest producer.

To extract the metal, the sulfide is roasted in air to give the oxide, and the oxide is then reduced with carbon. Part of it comes from recycling, mostly from old lead batteries. Because antimony was known in antiquity, there is no year of discovery. The symbol Sb comes from the Latin stibium, the old word for the mineral.

Ground stibnite was used as black eye makeup as early as antiquity, in Egypt alongside galena. Kohl and kajal, the dark lines around the eyes, recall this tradition. In the Middle Ages and the early modern period, alchemists and physicians used antimony compounds, for example tartar emetic, which induces vomiting. Today it is known that many of these remedies caused poisoning.

Properties and reactions

Antimony is in period 5 and group 15, below arsenic and above bismuth. In the period, tin lies to its left and tellurium to its right. Its electron configuration is [Kr] 4d¹⁰ 5s² 5p³ and its electronegativity is 2.05. The element has 5 valence electrons. The density is 6.685 g/cm³, the melting point 630.63 °C and the boiling point 1587 °C.

Antimony is a metalloid. It shines like a metal and conducts electricity, but only moderately. It is brittle and can be ground to a powder. Like water, liquid antimony expands slightly as it solidifies. The metal is stable in air at room temperature. In a flame it burns to antimony trioxide, Sb₂O₃, a white smoke. In compounds the oxidation numbers plus three and plus five are the most common. Antimony oxide reacts with both acids and alkalis, so it is amphoteric.

Antimony and its compounds are toxic. Larger amounts cause nausea, vomiting and damage to the heart and liver, a picture similar to arsenic poisoning. Antimony trioxide is suspected of causing cancer when its dust is inhaled. Antimony compounds therefore do not belong in school experiments.

Uses in everyday life and technology

Most antimony goes into flame retardants as antimony trioxide. Together with bromine-containing substances, it keeps plastics in cables, housings and upholstery from catching fire easily. The same oxide serves as a catalyst in making PET, the plastic of many drink bottles.

As an alloying metal, antimony hardens soft lead. The alloy is called hard lead and was used in the plates of lead-acid batteries such as car batteries. The type metal of letterpress printers also consists of lead, antimony and tin. The melt expands as it solidifies and fills the mould right into the finest edges, so the letters stayed sharp. Antimony also hardens bearing metals and pewter-type tin alloys.

In electronics, antimony and indium form the semiconductor indium antimonide, which detects infrared radiation. Compounds of antimony, tellurium and germanium are used in data storage such as rewritable optical discs, because laser light can switch their crystal structure. Antimony is also added to silicon semiconductors as a dopant that supplies electrons as charge carriers.

The EU counts antimony as a critical raw material, because mining is concentrated in a few countries.

Molecules containing this element

• Antimony(III) oxide Sb₂O₃View in 3D
• Antimony(III,V) oxide Sb₂O₄View in 3D
• Antimony(V) oxide Sb₂O₅View in 3D

Quick question

What is the atomic number of antimony (Sb)?

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