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Thallium,  81Tl
Thallium pieces in ampoule.jpg
General properties
Name, seembol thallium, Tl
Pronunciation /ˈθæliəm/
Appearance sillery white
Thallium in the periodic cairt
Hydrogen (diatomic nonmetal)
Helium (noble gas)
Lithium (alkali metal)
Beryllium (alkaline yird metal)
Boron (metalloid)
Carbon (polyatomic nonmetal)
Nitrogen (diatomic nonmetal)
Oxygen (diatomic nonmetal)
Fluorine (diatomic nonmetal)
Neon (noble gas)
Sodium (alkali metal)
Magnesium (alkaline yird metal)
Aluminium (post-transeetion metal)
Silicon (metalloid)
Phosphorus (polyatomic nonmetal)
Sulfur (polyatomic nonmetal)
Chlorine (diatomic nonmetal)
Argon (noble gas)
Potassium (alkali metal)
Calcium (alkaline yird metal)
Scandium (transeetion metal)
Titanium (transeetion metal)
Vanadium (transeetion metal)
Chromium (transeetion metal)
Manganese (transeetion metal)
Iron (transeetion metal)
Cobalt (transeetion metal)
Nickel (transeetion metal)
Copper (transeetion metal)
Zinc (transeetion metal)
Gallium (post-transeetion metal)
Germanium (metalloid)
Arsenic (metalloid)
Selenium (polyatomic nonmetal)
Bromine (diatomic nonmetal)
Krypton (noble gas)
Rubidium (alkali metal)
Strontium (alkaline yird metal)
Yttrium (transeetion metal)
Zirconium (transeetion metal)
Niobium (transeetion metal)
Molybdenum (transeetion metal)
Technetium (transeetion metal)
Ruthenium (transeetion metal)
Rhodium (transeetion metal)
Palladium (transeetion metal)
Silver (transeetion metal)
Cadmium (transeetion metal)
Indium (post-transeetion metal)
Tin (post-transeetion metal)
Antimony (metalloid)
Tellurium (metalloid)
Iodine (diatomic nonmetal)
Xenon (noble gas)
Caesium (alkali metal)
Barium (alkaline yird metal)
Lanthanum (lanthanide)
Cerium (lanthanide)
Praseodymium (lanthanide)
Neodymium (lanthanide)
Promethium (lanthanide)
Samarium (lanthanide)
Europium (lanthanide)
Gadolinium (lanthanide)
Terbium (lanthanide)
Dysprosium (lanthanide)
Holmium (lanthanide)
Erbium (lanthanide)
Thulium (lanthanide)
Ytterbium (lanthanide)
Lutetium (lanthanide)
Hafnium (transeetion metal)
Tantalum (transeetion metal)
Tungsten (transeetion metal)
Rhenium (transeetion metal)
Osmium (transeetion metal)
Iridium (transeetion metal)
Platinum (transeetion metal)
Gold (transeetion metal)
Mercury (transeetion metal)
Thallium (post-transeetion metal)
Lead (post-transeetion metal)
Bismuth (post-transeetion metal)
Polonium (post-transeetion metal)
Astatine (metalloid)
Radon (noble gas)
Francium (alkali metal)
Radium (alkaline yird metal)
Actinium (actinide)
Thorium (actinide)
Protactinium (actinide)
Uranium (actinide)
Neptunium (actinide)
Plutonium (actinide)
Americium (actinide)
Curium (actinide)
Berkelium (actinide)
Californium (actinide)
Einsteinium (actinide)
Fermium (actinide)
Mendelevium (actinide)
Nobelium (actinide)
Lawrencium (actinide)
Rutherfordium (transeetion metal)
Dubnium (transeetion metal)
Seaborgium (transeetion metal)
Bohrium (transeetion metal)
Hassium (transeetion metal)
Meitnerium (unkent chemical properties)
Darmstadtium (unkent chemical properties)
Roentgenium (unkent chemical properties)
Copernicium (transeetion metal)
Ununtrium (unkent chemical properties)
Flerovium (post-transeetion metal)
Ununpentium (unkent chemical properties)
Livermorium (unkent chemical properties)
Ununseptium (unkent chemical properties)
Ununoctium (unkent chemical properties)


Atomic nummer 81
Staundart atomic wicht (±) (Ar) 204.38(1)
Element category   poor metal
Group, block group 13, p-block
Period period 6
Electron configuration [Xe] 4f14 5d10 6s2 6p1
per shell
2, 8, 18, 32, 18, 3
Pheesical properties
Phase solid
Meltin pynt 577 K ​(304 °C, ​579 °F)
Boilin pynt 1746 K ​(1473 °C, ​2683 °F)
Density near r.t. 11.85 g/cm3
when liquid, at m.p. 11.22 g/cm3
Heat o fusion 4.14 kJ/mol
Heat o 165 kJ/mol
Molar heat capacity 26.32 J/(mol·K)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 882 977 1097 1252 1461 1758
Atomic properties
Oxidation states

3, 2, 1

(mildly basic oxide)
Electronegativity Pauling scale: 1.62
Atomic radius empirical: 170 pm
Covalent radius 145±7 pm
Van der Waals radius 196 pm
Crystal structur hexagonal close-packed (hcp)
Hexagonal close packed crystal structure for thallium
Speed o soond thin rod 818 m/s (at 20 °C)
Thermal expansion 29.9 µm/(m·K) (at 25 °C)
Thermal conductivity 46.1 W/(m·K)
Electrical resistivity 0.18 µ Ω·m (at 20 °C)
Magnetic orderin diamagnetic[1]
Young's modulus 8 GPa
Shear modulus 2.8 GPa
Bulk modulus 43 GPa
Poisson ratio 0.45
Mohs haurdness 1.2
Brinell haurdness 26.4 MPa
CAS Registry Nummer 7440-28-0
Discovery William Crookes (1861)
First isolation Claude-Auguste Lamy (1862)
Maist stable isotopes
Main article: Isotopes o thallium
iso NA hauf-life DM DE (MeV) DP
203Tl 29.524% - (α) 0.9108 199Au
204Tl syn 3.78 y β 0.764 204Pb
ε 0.347 204Hg
205Tl 70.476% - (α) 0.1567 201Au
Decay modes in parentheses are predictit, but hae nae yet been observed
· references

Thallium is a chemical element wi seembol Tl an atomic nummer 81. This saft gray poor metal is nae foond free in naitur. When isolated, it resembles tin, but discolors when exposed tae air. Chemists William Crookes an Claude-Auguste Lamy discovered thallium independently in 1861, in residues o sulfuric acid production. Baith uised the newly developed method o flame spectroscopy, in which thallium produces a notable green spectral line. Thallium, frae Greek θαλλός, thallos, meanin "a green shuit or twig," wis named bi Crookes. It wis isolatit bi electrolysis a year later, bi Lamy.

References[eedit | eedit soorce]

  1. Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.