Thallium

Thallium, 81Tl
Thallium
Pronunciation/ˈθæliəm/ (THAL-ee-əm)
Appearancesilvery white
Standard atomic weight Ar°(Tl)
Thallium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
In

Tl

Nh
mercurythalliumlead
Atomic number (Z)81
Groupgroup 13 (boron group)
Periodperiod 6
Block  p-block
Electron configuration[Xe] 4f14 5d10 6s2 6p1
Electrons per shell2, 8, 18, 32, 18, 3
Physical properties
Phase at STPsolid
Melting point577 K ​(304 °C, ​579 °F)
Boiling point1746 K ​(1473 °C, ​2683 °F)
Density (near r.t.)11.85 g/cm3
when liquid (at m.p.)11.22 g/cm3
Heat of fusion4.14 kJ/mol
Heat of vaporization165 kJ/mol
Molar heat capacity26.32 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 882 977 1097 1252 1461 1758
Atomic properties
Oxidation states−5,[3] −2, −1, +1, +2, +3 (a mildly basic oxide)
ElectronegativityPauling scale: 1.62
Ionization energies
  • 1st: 589.4 kJ/mol
  • 2nd: 1971 kJ/mol
  • 3rd: 2878 kJ/mol
Atomic radiusempirical: 170 pm
Covalent radius145±7 pm
Van der Waals radius196 pm
Color lines in a spectral range
Spectral lines of thallium
Other properties
Natural occurrenceprimordial
Crystal structurehexagonal close-packed (hcp)
Hexagonal close packed crystal structure for thallium
Thermal expansion29.9 µm/(m⋅K) (at 25 °C)
Thermal conductivity46.1 W/(m⋅K)
Electrical resistivity0.18 µΩ⋅m (at 20 °C)
Magnetic orderingdiamagnetic[4]
Molar magnetic susceptibility−50.9×10−6 cm3/mol (298 K)[5]
Young's modulus8 GPa
Shear modulus2.8 GPa
Bulk modulus43 GPa
Speed of sound thin rod818 m/s (at 20 °C)
Poisson ratio0.45
Mohs hardness1.2
Brinell hardness26.5–44.7 MPa
CAS Number7440-28-0
History
Namingafter Greek thallos, green shoot or twig
DiscoveryWilliam Crookes (1861)
First isolationClaude-Auguste Lamy (1862)
Isotopes of thallium
Main isotopes[6] Decay
abun­dance half-life (t1/2) mode pro­duct
201Tl synth 3.0421 d ε 201Hg
203Tl 29.5% stable
204Tl synth 3.78 y β 204Pb
ε + β+ 204Hg
205Tl 70.5% stable
 Category: Thallium
| references

Thallium is a chemical element; it has symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861, in residues of sulfuric acid production. Both used the newly developed method of flame spectroscopy, in which thallium produces a notable green spectral line. Thallium, from Greek θαλλός, thallós, 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 international exhibition, which opened on 1 May that year.[7]

Thallium tends to form the +3 and +1 oxidation states. The +3 state resembles that of the other elements in group 13 (boron, aluminium, gallium, indium). However, the +1 state, which is far more prominent in thallium than the elements above it, recalls the chemistry of alkali metals, 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 ion pumps 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 electronics industry, and the remainder is used in the pharmaceutical industry and in glass manufacturing.[8] It is also used in infrared detectors. The radioisotope thallium-201 (as the soluble chloride TlCl) is used in small amounts as an agent in a nuclear medicine scan, during one type of nuclear cardiac stress test.

Soluble thallium salts (many of which are nearly tasteless) are highly toxic, and they were historically used in rat poisons and insecticides. 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 arsenic).[9]

  1. ^ "Standard Atomic Weights: Thallium". CIAAW. 2009.
  2. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  3. ^ Dong, Z.-C.; Corbett, J. D. (1996). "Na23K9Tl15.3: An Unusual Zintl Compound Containing Apparent Tl57−, Tl48−, Tl37−, and Tl5− Anions". Inorganic Chemistry. 35 (11): 3107–12. doi:10.1021/ic960014z. PMID 11666505.
  4. ^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  5. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  6. ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  7. ^ The Mining and Smelting Magazine Archived 2021-02-24 at the Wayback Machine. Ed. Henry Curwen Salmon. Vol. iv, July–Dec 1963, p. 87.
  8. ^ Cite error: The named reference sl2001 was invoked but never defined (see the help page).
  9. ^ Hasan, Heather (2009). The Boron Elements: Boron, Aluminum, Gallium, Indium, Thallium. Rosen Publishing Group. p. 14. ISBN 978-1-4358-5333-1.