90Th232.04

Thorium (Th) – element 90

Thorium is a chemical element with the symbol Th and atomic number 90. It is a actinide in group 3 (actinides), period 7 of the periodic table (f-block), and is a solid at room temperature.

Thorium (Th) has atomic number 90, atomic mass 232.04 u and electron configuration [Rn] 6d2 7s2.

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Thorium facts

SymbolTh
Atomic number90
Atomic mass232.04 u (g/mol)
Categoryactinide
Groupgroup 3 (actinides)
Period7
Blockf-block
Phase at 20 °CSolid
Electron configuration1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 6d2
Noble-gas notation[Rn] 6d2 7s2
Electrons per shell2, 8, 18, 32, 18, 10, 2

Bohr model and shells

Th

Thorium has 90 electrons in 7 shells: 2, 8, 18, 32, 18, 10, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the electron configuration calculator.

Physical and atomic properties

Melting point2023 K (1749.8 °C)
Boiling point5061 K (4787.9 °C)
Density11.724 g/cm³
Electronegativity (Pauling)1.3
Electron affinity112.72 kJ/mol
Ionization energies587, 1110, 1930 kJ/mol (1st, 2nd, 3rd)
Molar heat capacity26.23 J/(mol·K)
Discovered byJöns Jakob Berzelius

Use the atomic mass in the molar mass calculator for any formula containing Th.

Position in the periodic table

HydrogenHHeliumHeLithiumLiBerylliumBeBoronBCarbonCNitrogenNOxygenOFluorineFNeonNeSodiumNaMagnesiumMgAluminiumAlSiliconSiPhosphorusPSulfurSChlorineClArgonArPotassiumKCalciumCaScandiumScTitaniumTiVanadiumVChromiumCrManganeseMnIronFeCobaltCoNickelNiCopperCuZincZnGalliumGaGermaniumGeArsenicAsSeleniumSeBromineBrKryptonKrRubidiumRbStrontiumSrYttriumYZirconiumZrNiobiumNbMolybdenumMoTechnetiumTcRutheniumRuRhodiumRhPalladiumPdSilverAgCadmiumCdIndiumInTinSnAntimonySbTelluriumTeIodineIXenonXeCesiumCsBariumBaLanthanumLaCeriumCePraseodymiumPrNeodymiumNdPromethiumPmSamariumSmEuropiumEuGadoliniumGdTerbiumTbDysprosiumDyHolmiumHoErbiumErThuliumTmYtterbiumYbLutetiumLuHafniumHfTantalumTaTungstenWRheniumReOsmiumOsIridiumIrPlatinumPtGoldAuMercuryHgThalliumTlLeadPbBismuthBiPoloniumPoAstatineAtRadonRnFranciumFrRadiumRaActiniumAcThoriumThProtactiniumPaUraniumUNeptuniumNpPlutoniumPuAmericiumAmCuriumCmBerkeliumBkCaliforniumCfEinsteiniumEsFermiumFmMendeleviumMdNobeliumNoLawrenciumLrRutherfordiumRfDubniumDbSeaborgiumSgBohriumBhHassiumHsMeitneriumMtDarmstadtiumDsRoentgeniumRgCoperniciumCnNihoniumNhFleroviumFlMoscoviumMcLivermoriumLvTennessineTsOganessonOg

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Frequently asked questions

What is the atomic mass of thorium?

The atomic mass of thorium is 232.04 u, so one mole of thorium atoms weighs 232.04 g.

What is the electron configuration of thorium?

Thorium has 90 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 6d², or [Rn] 6d² 7s² in noble-gas notation. Electrons per shell: 2, 8, 18, 32, 18, 10, 2.

Is thorium a metal?

Yes. Thorium is a actinide.

Where is thorium on the periodic table?

Thorium is in group 3 (actinides), period 7, in the f-block.

Data: Periodic-Table-JSON (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.