Thorium

Chemical, physical and material properties and data of the chemical element Thorium.

Contents

Thorium is a chemical element from the actinide group and, in its pure form, is a silvery metal that only very slowly - over a period of weeks or months - loses its luster due to the formation of an oxide layer.

Thorium was discovered in the 19th century by the Swedish chemist Jöns Jacob Berzelius and isolated in 1828 by the German chemist Wilhelm Körner. It has long been used as an alloying agent in gas lamps, but also as a catalyst in the chemical industry and as a stabilizer in plastics.

In recent years, thorium has also been discussed as a possible energy carrier in nuclear reactors, as it can be used as a fuel in so-called thorium fuel cells. These types of reactors would produce less harmful waste than conventional nuclear reactors and might also be able to utilize radioactive waste from other nuclear reactors. However, there are also concerns about safety - due to its radioactivity and toxicity - and the technology development needed to use thorium fuel cells.

General Information about Thorium

Regular nameThoriumChemical symbolThOther namesElement 90Historical namesIonium (Th-230); Donarium (Dt), Wasmium (Wa) (all formerly used); Carolinium (erroneously)Name meaning, originThor - Germanic godDiscovery (year)(1829) - Jons Jakob Berzelius, Esmark.OccurenceThorium occurs in the earth's crust at a frequency of 7 to 13 mg per kg; it is therefore twice to three times as common as uraniumPosition in the PSEActinides, period 7, f-blockGroup membershipMetals

Atomar Properties of Thorium

Atomic number Z90 = number of protonsStandard Atomic Weight232.0377 (4)

Electron configuration of Thorium

1s	2s	2p	3s	3p	3d	4s	4p	4d	4f	5s	5p	5d	5f	6s	6p	6d	6f	7s	7p
2	2	6	2	6	10	2	6	10	14	2	6	10		2	6	2		2

Shorthand electron configuration of Thorium: [Rn] 6d² 7s² .

Ionization Energies of Thorium

The following table lists the ionization energies IE (ionization potentials); the IE is the energy required in electron volt (eV) per atom to separate a given electron from an Thorium atom.

IE1	IE2	IE3	IE4
6.3067	11.9	20.0	28.8

Isotopic Data of Thorium

An overview of the nuclides as well as the isotopic data and properties are listed on the following page: Thorium isotopes.

Chemistry of Thorium

Valence electrons4Oxidation states+ 4Electronegativity1.3 (Pauling original)
1.30 (Pauling)Electron affinity1.17 eV
112.72 kJ mol^-1

Standard Electrode Potential

E⁰ (V)	Symbol	N_ox	Name Ox. Name Red.	Ox. Red.	e^-
-2.48	Th	+ IV 0	Thorium(IV) hydroxide Thorium	Th(OH)₄ ⇄ Th + 4 OH^-	+ 4 e^-
-1.899	Th	+ IV 0	Thorium(IV) cation Thorium	Th⁴⁺ ⇄ Th	+ 4 e^-
-1.789	Th	+ IV 0	Thorium(IV) oxide Thorium	ThO₂ + 4 H⁺ ⇄ Th + 2 H₂O	+ 4 e^-

Material and Physical Properties

Melting point1750 °CEnthalpy of fusion (molar)13.81 kJ mol^-1Boiling point4785 °CEnthalpy of vaporization543.9 kJ mol^-1Density11.724 g cm^-3

External Data, Identifiers

CAS registry number7440-29-1InChI =1S/ThInChIKeyZSLUVFAKFWKJRC-UHFFFAOYSA-NPubChem ID23960

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Last update: 2022-12-16

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