Thallium is at chemical element , it has symbol Tl and atomic number 81. Its standard atomic weight is 204.4. It is found in Group 15 of the periodic table. Thallium is a soft, heavy and gray metal, but can look red due to oxidation . Thallium and its compounds are extremely toxic, even more than cyanide and arsenic .
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Thallium, 81 Tl Pronunciation (THAL -ee-əm ) Appearance silvery white [ 204.382 , 204.385 ][1]
Atomic number (Z ) 81 Group group 13 (boron group) Period period 6 Block p-block Electron configuration [ Xe ] 4f14 5d10 6s2 6p1 Electrons per shell 2, 8, 18, 32, 18, 3 Phase at STP solid Melting point 577 K (304 °C, 579 °F) Boiling point 1746 K (1473 °C, 2683 °F) Density (near r.t. ) 11.85 g/cm3 when liquid (at m.p. ) 11.22 g/cm3 Heat of fusion 4.14 kJ/mol Heat of vaporization 165 kJ/mol Molar heat capacity 26.32 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
Oxidation states −5,[2] −2, −1, +1 , +2, +3 (a mildly basic oxide) Electronegativity Pauling scale: 1.62 Ionization energies 1st: 589.4 kJ/mol 2nd: 1971 kJ/mol 3rd: 2878 kJ/mol Atomic radius empirical: 170 pm Covalent radius 145±7 pm Van der Waals radius 196 pm Spectral lines of thalliumNatural occurrence primordial Crystal structure hexagonal close-packed (hcp)Speed of sound 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 µΩ⋅m (at 20 °C) Magnetic ordering diamagnetic [3] Molar magnetic susceptibility −50.9× 10−6 cm3 /mol (298 K)[4] Young's modulus 8 GPa Shear modulus 2.8 GPa Bulk modulus 43 GPa Poisson ratio 0.45 Mohs hardness 1.2 Brinell hardness 26.5–44.7 MPa CAS Number 7440-28-0 Naming after Greek thallos , green shoot or twig Discovery William Crookes (1861)First isolation Claude-Auguste Lamy (1862)
Main isotopes[5]
Decay
abun dance
half-life (t 1/2 )
mode
pro duct
201 Tl
synth
3.0421 d
ε
201 Hg
203 Tl
29.5%
stable
204 Tl
synth
3.78 y
β−
204 Pb
ε + β+
204 Hg
205 Tl
70.5%
stable
Category: Thallium | references
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