General | States | Energies | Oxidation & Electrons |Appearance & Characteristics
Reactions | Other Forms |Radius | Conductivity | Abundance
Encyclopedia Britannica articles


Name Thallium Symbol Tl
atomic number 81 Atomic weight 204.37
Density @ 293 K 11.85 g/cm3 Atomic volume 17.2 cm3/mol
Group Metal discovered 1861


state (s, l, g) s
melting point 576.7 K boiling point 1730 K
Heat of fusion 4.142 kJ/mol Heat of vaporization 164.10 kJ/mol
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1st ionization energy 589.4 kJ/mole electronegativity 1.83
2nd ionization energy 1971 kJ/mole electron affinity 20 kJ/mole
3rd ionization energy 2878 kJ/mole Specific heat 0.13 J/gK
heat atomization 182 kJ/mole atoms

Oxidation & Electrons

Shells 2,8,18,32,18,3 electron configuration [Xe] 4f14 5d10 6s2 6p1
minimum oxidation number 0 maximum oxidation number 3
min. common oxidation no. 0 max. common oxidation no. 3
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Appearance & Characteristics

structure hcp: hexagonal close pkd color bluish-gray
uses IR detectors, photomult. toxicity
hardness 1.2 mohs characteristics soft


reaction with air mild, = Tl2O reaction with 6M HCl
reaction with 6M HCl reaction with 15M HNO3 mild, = TlNO3
reaction with 6M NaOH
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Other Forms

number of isotopes 2 hydride(s)
oxide(s) Tl2O Tl2O3 chloride(s) TlCl TlCl3


ionic radius (2- ion) pm ionic radius (1- ion) pm
atomic radius 170 pm ionic radius (1+ ion) 164 pm
ionic radius (2+ ion) pm ionic radius (3+ ion) 102.5 pm
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thermal conductivity 46.1 J/m-sec-deg electrical conductivity 55.556 1/mohm-cm
polarizability 7.6 A^3


source Zn/Pb smelting by-product rel. abund. solar system -0.735 log
abundance earth's crust -0.3 log cost, pure 48 $/100g
cost, bulk $/100g
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World Wide Web presentation of Chemicool Periodic Table is © Copyright 1996-99 by David D. Hsu. Some data were provided by and used with the permission of JCE Software and is owned and copyright by the Division of Chemical Education, Inc. Additional data were provided by Perkin-Elmer through Peter Lykos of IIT. The information may not be redistributed without the permission of David Hsu or JCE Software.