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


Name Thorium Symbol Th
atomic number 90 Atomic weight 232.0381
Density @ 293 K 11.7 g/cm3 Atomic volume 19.9 cm3/mol
Group Rare Earth, Actinides discovered 1829


state (s, l, g) s
melting point 2023.2 K boiling point 5123 K
Heat of fusion 16.10 kJ/mol Heat of vaporization 514.40 kJ/mol
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1st ionization energy 587 kJ/mole electronegativity 1.3
2nd ionization energy 1110 kJ/mole electron affinity kJ/mole
3rd ionization energy 1930 kJ/mole Specific heat 0.12 J/gK
heat atomization 576 kJ/mole atoms

Oxidation & Electrons

Shells 2,8,18,32,18,10,2 electron configuration [Rn] 6d2 7s2
minimum oxidation number 0 maximum oxidation number 4
min. common oxidation no. 0 max. common oxidation no. 4
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Appearance & Characteristics

structure fcc: face-centered cubic color white
uses gas mantles (ThO2) toxicity
hardness mohs characteristics Radioactive


reaction with air mild, w/ht ignites = ThO2 reaction with 6M HCl mild
reaction with 6M HCl mild reaction with 15M HNO3 passivated
reaction with 6M NaOH none
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Other Forms

number of isotopes 3 hydride(s) ThH2 Th4H15
oxide(s) ThO2 chloride(s) ThCl4


ionic radius (2- ion) pm ionic radius (1- ion) pm
atomic radius 179 pm ionic radius (1+ ion) pm
ionic radius (2+ ion) pm ionic radius (3+ ion) pm
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thermal conductivity 54 J/m-sec-deg electrical conductivity 76.923 1/mohm-cm
polarizability 32.1 A^3


source Monazite(phosphate),U extractn rel. abund. solar system -1.475 log
abundance earth's crust 1 log cost, pure $/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.