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sillery white
General properties
Name, seembol, nummer thallium, Tl, 81
Pronunciation /ˈθæliəm/
Element category poor metal
Group, period, block 13, 6, p
Staundart atomic wicht 204.38(1)
Electron confeeguration [Xe] 4f14 5d10 6s2 6p1
2, 8, 18, 32, 18, 3
Electron shells of thallium (2, 8, 18, 32, 18, 3)
Discovery William Crookes (1861)
First isolation Claude-Auguste Lamy (1862)
Physical properties
Phase solid
Density (near r.t.) 11.85 g·cm−3
Liquid density at m.p. 11.22 g·cm−3
Meltin pynt 577 K, 304 °C, 579 °F
Boilin pynt 1746 K, 1473 °C, 2683 °F
Heat o fusion 4.14 kJ·mol−1
Heat o vaporization 165 kJ·mol−1
Molar heat capacity 26.32 J·mol−1·K−1
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 3, 2, 1

(mildly basic oxide)

Electronegativity 1.62 (Pauling scale)
Ionization energies 1st: 589.4 kJ·mol−1
2nd: 1971 kJ·mol−1
3rd: 2878 kJ·mol−1
Atomic radius 170 pm
Covalent radius 145±7 pm
Van der Waals radius 196 pm
Crystal structure hexagonal close-packed
Thallium has a hexagonal close packed crystal structure
Magnetic orderin diamagnetic[1]
Electrical resistivity (20 °C) 0.18 µΩ·m
Thermal conductivity 46.1 W·m−1·K−1
Thermal expansion (25 °C) 29.9 µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 818 m·s−1
Young's modulus 8 GPa
Shear modulus 2.8 GPa
Bulk modulus 43 GPa
Poisson ratio 0.45
Mohs hairdness 1.2
Brinell hairdness 26.4 MPa
CAS registry nummer 7440-28-0
Most 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
· r

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.