81 Tl (Thallium)
Appearance: Silvery white
Mass number: 204
Standard Atomic weight: 204.38 g/mol
Atomic number (Z): 81
Electrons: 81
Protons: 81
Neutrons: 123
Group: 13
Period: 6
Block: p
Element category: Post-transition metal
Electrons per shell: K2, L8, M18, N32, O18, P3
Electron Configuration: 1s22s22p63s23p63d104s24p64d105s25p64f145d106s26p1
Phase: solid
Melting point: 577 K (304 oC)
Boiling point: 1746 K (1473 oC)
Density: 11.85 g/cm3 (in solid) , 11.22 g/cm3(in Liquid at m.p)
Neutron cross section (Brans): 3.4
Heat of fusion: 4.14 kJ/mol
Heat of vaporization: 165 kJ/mol
Molar heat capacity: 26.32 J/(mol∙K)
Molar volume: 0.000017248
Oxidation states: 3, 2, 1, -1, -2, -5
Ion charge: Tl+, Tl3+
Electronegativity: pauling scale; 1.62
Valence: 3
Electron affinity: 19.2 kJ/mol
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
Vander waals radius: 196 pm
Crystal structure: Hexagonal close-packed
Grid parameters: a=3.456 c=5.525
Attitude c/a: 1.599
Debye temperature: 96 K (-177.15 oC)
Sound speed: 818 m/s
Thermal expansion: 29.9 μm/(m∙K)
Thermal conductivity: 46.1 W/(m∙K)
Electrical resistivity: 0.18 μΩ∙m
Magnetic ordering: Diamagnetic
Magnetic Susceptibility: -50.9×10-6 cm3/mol
Volume magnetic susceptibility: -0.0000356
Mass magnetic susceptibility: -3×10-9 m3/kg
Molar magnetic susceptibility: -6.13×10-10 m3/mol
Superconducting point: 2.38 K (270.77 oC)
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
Discovery: William Crookes (1861)
First isolation: Claude-Auguste Lamy (1862)
Isotopes: 203Tl 204Tl 205Tl
Uses of Thallium:
Thallium sulfate was employed as a rodent(Rat) killer, Household use this poison has been prohibited in most developed countries. Thallium is mostly used photoelectric cells and Thallium oxide is used to produce special glass with a high index refrection.
Biological role of Thallium:
It is very toxic and there is evidence that the vapour is both teratogenic and carcinogenic. It can affecting the central nervous system of body.
Natural abundance:
It is found in several ores like pyrites, which is used to produce sulphuric acid. But Thallium is mainly obtained as a by-product of copper, zinc and lead refining. Thallium is also present in manganese nodules found on the ocean floor.
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