Antimony

Antimony is a lustrous, silvery-grey metalloid in group 15, below arsenic and above bismuth. Its configuration, [Kr] 4d10 5s2 5p3, gives it five valence electrons and common oxidation states of +3 and +5, with −3 in metal antimonides. Its properties sit between metal and non-metal: it looks metallic but is brittle enough to crush to powder, and it conducts electricity and heat poorly. In its stable form the atoms bond into puckered layers, each atom joined to three neighbours, which explains both the brittleness and the flaky, crystalline fracture of the solid.

Like water, molten antimony expands slightly as it freezes. Printers exploited this for centuries: type metal, an alloy of lead, tin and antimony, swells into every corner of the mould and gives crisp letters. Antimony also hardens the lead grids of car batteries. The largest modern use is antimony trioxide, which is combined with halogenated compounds to make plastics, textiles and electronics resist burning; it interrupts the radical chain reactions in a flame. Antimony trioxide is also the catalyst for most PET plastic bottles. China dominates production, and the EU and the US list antimony as a critical raw material.

Discovery

Antimony sulfide, the mineral stibnite, was ground into black kohl eye cosmetic in ancient Egypt, and a vase of nearly pure antimony from about 3000 BCE was found at Tello in Iraq. The Latin name stibium gave the symbol Sb. The origin of 'antimony' is uncertain; one popular but doubtful story derives it from the French anti-moine, 'monk-killer'. Vannoccio Biringuccio described how to extract the metal in 1540, and in 1615 Andreas Libavius published a method using iron to reduce the sulfide.