81 204.380

Thallium , Tl

Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray malleable poor metal resembles tin but discolors when exposed to air. Approximately 60-70% of thallium production is used in the electronics industry, and the rest is used in the pharmaceutical industry and in glass manufacturing. It is used in infrared detectors. Thallium is highly toxic and is used in rat poisons and insecticides. Since it may cause cancer[citation needed] (although the United States EPA does not class it as carcinogen), its use has been cut back or eliminated in many countries. It is used in murders and has the nicknames "The Poisoner's Poison" and "Inheritance powder" (alongside arsenic).


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Thallium (I) Chloride TlCl -20 mesh 99.999% pure

TlCl -20 mesh 99.9% Pure

Thallium (I) Chloride UN1707 6.1 PG II


TlF -8 mesh 99.9% Pure

Thallium (I) Fluoride UN1707 6.1 PG II


TlF3 -4 mesh 99.9% Pure

Thallium (II) Fluoride UN1707 6.1 PG II

Thallium (I) Nitrate TlNO3 -40 mesh 99.999% pure

TlNO3 -40 mesh 99.5% Pure

Thallium (I) Nitrate UN2727 6.1 PG II

Thallium (III) Oxide Tl2O3 -20 mesh 99.999% pure

Tl2O3 -20 mesh 99.5% Pure

Thallium (III) Oxide UN1707 6.1 PG II

Thallium (I) Sulphate Tl2SO4 -4 mesh 99.999% pure
Thallium (I) Sulphate Tl2SO4 -4 mesh 99.99% pure

Tl2S -20 mesh 99.9% Pure

Thallium (I) Sulphide UN1707 6.1 PG II


Tl Rod 12.7mm diameter 99.9% pure


This metal is very soft and malleable and can be cut with a knife. When it is first exposed to air, thallium has a metallic luster but quickly tarnishes with a bluish-gray tinge that resembles lead (it is preserved by keeping it under oil). A heavy layer of oxide builds up on thallium if left in air. In the presence of water, thallium hydroxide is formed.

Symbol Tl
Atomic number 81
No. of naturally occurring isotopes 2
Atomic weight 204.383
Electronic configuration [Xe]4f145d106s26p1
Metal radius(6-coordinate)/pm 170
Ionic radius(6-coordinate)/pm III 88.5
Ionic radius(6-coordinate)/pm I 150
E° (M3+(aq)\ + 3e- →M(s))/V 1.26
E° (M+(aq)\ + e- →M(s))/V -0.34
Electronegativity χ 1.8
Density (20°C)/gcm3 11.85
Melting point / °C 303.5
Boiling point / °C 1457
ΔHfus/kJmol-1 4.31
ΔHvap/kJmol-1 166.1
ΔHf(monoatomic gas)/kJmol-1 180.7
Electrical resistivity (20°C)/μohm cm 18
Ionization energy/kJmol-1 I 589.1
Ionization energy/kJmol-1 II 1970.5
Ionization energy/kJmol-1 III 2877.4
Hardness (Mohs) 1.2-1.3
Temperature (oC) @Vap. Pressure
10-8 Torr 280
10-6 Torr 360
10-4 Torr 470
Electron Beam Poor
Crucible Al2O3 & Quartz
Coil -
Boat Tungsten & Tantalum
Wets freely, very toxic