Thallium

Thallium is a <a href="/facts/Chemical_element/0jducgWD">chemical element</a>; it has <a href="/facts/Symbol_(chemistry)/2Fe1VAL0">symbol</a> Tl and <a href="/facts/Atomic_number/bgAr581S">atomic number</a> 81. It is a silvery-white <a href="/facts/Post-transition_metal/wjp3aeGn">post-transition metal</a> that is not found free in nature. When isolated, thallium resembles <a href="/facts/Tin/obW9mqc3">tin</a>, but discolors when exposed to air. Chemists <a href="/facts/William_Crookes/q8U8VVwR">William Crookes</a> and <a href="/facts/Claude-Auguste_Lamy/rHGVVGHW">Claude-Auguste Lamy</a> discovered thallium independently, in 1861, in residues of <a href="/facts/Sulfuric_acid/Wom6fymJ">sulfuric acid</a> production. Both used the newly developed method of <a href="/facts/Flame_spectroscopy/5s0wg1sX">flame spectroscopy</a>, in which thallium produces a notable green spectral line. Thallium, from <a href="/facts/Greek_language/pzDd6eIz">Greek</a> θαλλός, <a href="/facts/Thallus/4FbF7wmC">thallós</a>, meaning "green shoot" or "twig", was named by Crookes. It was isolated by both Lamy and Crookes in 1862, Lamy by electrolysis and Crookes by precipitation and melting of the resultant powder. Crookes exhibited it as a powder precipitated by zinc at the <a href="/facts/1862_International_Exhibition/oyaykYwn">International Exhibition</a>, which opened on 1 May that year.
Thallium tends to form the +3 and +1 oxidation states. The +3 state resembles that of the other elements in <a href="/facts/Boron_Group/RXnvqnNk">group 13</a> (<a href="/facts/Boron/Pmwgd7Mf">boron</a>, <a href="/facts/Aluminium/7wmR8jYE">aluminium</a>, <a href="/facts/Gallium/EucevDs9">gallium</a>, <a href="/facts/Indium/zRq3stVb">indium</a>). However, the +1 state, which is far more prominent in thallium than the elements above it, recalls the chemistry of <a href="/facts/Alkali_metal/IkWbCLk2">alkali metals</a> and thallium(I) ions are found geologically mostly in potassium-based ores and (when ingested) are handled in many ways like potassium ions (K+) by <a href="/facts/Ion_transporter/x41gIvhr">ion pumps</a> in living cells.
Commercially, thallium is produced not from potassium ores, but as a byproduct from refining of heavy-metal sulfide ores. Approximately 65% of thallium production is used in the <a href="/facts/Electronics_industry/YX8VCvKC">electronics industry</a> and the remainder is used in the <a href="/facts/Pharmaceutical_industry/5mCITYys">pharmaceutical industry</a> and in <a href="/facts/Glass/hezRsAGf">glass manufacturing</a>. It is also used in <a href="/facts/Infrared_detector/pK7SfsEv">infrared detectors</a>. The radioisotope thallium-201 (as the soluble chloride TlCl) is used in small amounts as an agent in a <a href="/facts/Nuclear_medicine/L9Dzjd90">nuclear medicine</a> scan, during one type of nuclear <a href="/facts/Cardiac_stress_test/kL4ovnza">cardiac stress test</a>.
Soluble thallium salts (many of which are nearly tasteless) are highly <a href="/facts/Toxic/qa96rs60">toxic</a> and they were historically used in <a href="/facts/Rat_poison/unEUuByD">rat poisons</a> and <a href="/facts/Insecticide/1xYL3MSD">insecticides</a>. Because of their nonselective toxicity, use of these compounds has been restricted or banned in many countries. Thallium poisoning usually results in hair loss. Because of its historic popularity as a murder weapon, thallium has gained notoriety as "the poisoner's poison" and "inheritance powder" (alongside <a href="/facts/Arsenic/k1c4f44D">arsenic</a>).

Thallium open-in-new

Thallium