Thorium

Thorium ( /ˈθɔəriəm/ thohr-ee-əm) is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder. In nature, virtually all thorium is found thorium-232, and it decays by emitting an alpha particle, and has a half-life of about 14.05 billion years (other, trace-level isotopes of thorium are short-lived intermediates of decay chains). It is estimated to be ... More

Chemical Element

The 90th Element in the Periodic Table

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Actinium

Actinium ( /ækˈtɪniəm/ ak-tin-nee-əm) is a radioactive chemical element with the symbol Ac and atomic number 89, which was discovered in 1899. It was...

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Protactinium

Protactinium ( /ˌproʊtækˈtɪniəm/ proh-tak-tin-ee-əm) is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray metal...

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Symbol:

  • Th

Atomic mass:

Mass Uncertainty
  • 232.03806 u (3.853082E-16 µg )
  • 0.00002 u (3.3211E-23 µg )

Electronegativity (Pauling scale):

  • 1.3

Van der Waals radius:

  • 240 pm (0.00000945 )

Melting Point:

  • 1,754.85 °C (3190.76 °F )

Boiling Point:

  • 4,786.85 °C (8648.42 °F )

Chemical series:

Ionization Energy:

  • 6.3067 eV (0.0000063067 MeV )

Discovery Date:

  • 1828

Electron Configuration:

  • Rn 6d2 7s2
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