90 Thorium

In 1815, the Swedish chemist Jöns Jakob Berzelius (1779-1848) obtained a material which he regarded as a new earth. He assigned this to a new oxide and the corresponding metal name was intended to honor Thor, the ancient Scandinavian god of thunder (note). However, in 1824, it turned out that this supposedly new earth was Yttrium phosphate.

Four years later, Reverend Hans Morten Thrane Esmark (1801-1882) discovered a black mineral on the island of Løvø (Finsholm) near Brevik, Norway. "Han kaldte det op efter Guden Thor" and gave a sample of this material to his father Jens Esmark, a leading Norwegian old-earth geology professor. Professor Esmark was unable to identify it as any known mineral, so he in turn sent a specimen to Berzelius for examination. A chemical analysis of this mineral by Berzelius demonstrated that it contained almost 60% of a new earth which he reported as distinct from all others known. It appears that, in naming this new oxide thoria and the mineral which it was obtained thorite (ThSiO₄), Berzelius fully restores the dignity of Thor from the earlier near humiliation.

The discovery of Thorium was announced by Berzelius in a publication in 1829 (note).

In Orangite, a mineral very similar to Thorite, found in Langesundfjord near Brevik, C. Bergemann thought in 1851 to have found a new element, different from Thorium. He named it Donarium, after the German god of war (note). Shortly afterwards was found the Orangite was identical with Thorite and Donarium identical with Thorium.

In 1862 J.F. Bahr described a new metal oxide from a mineral Wasite found on the island of Rösholm near Stockholm. He named the new element Wasium (note). Just as the mineral, named after Wasa, or Vasa, the name of a former royal family of Sweden. Within a year Bahr himself rejected his discovery: it was probably Thorium.

In The Tech, the newspaper of the Massachusetts Institute of Technology, of 21 April 1908 was announced that "Dr. Baskerville, of the University of North Carolina, (...) has resolved thorium into two new elements. One of these he has named Carolinium, after the State; the other Berzelium, in honor of the great Swedish chemist." (note).

Isotopes with the historical name ...thorium-...

Name	Hist. symb.	Mod. symb.
Thorium	Th	²³²Th
Mesothorium 1 Thorium 1	MsTh₁	²²⁸Ra
Mesothorium 2 Thorium 2	MsTh₂	²²⁸Ac
Radiothorium Thorium 3	RdTh	²²⁸Th
Thorium Emanation Thoron	ThEm Tn	²²⁰Rn
Thorium-A	Th A	²¹⁶Po
Thorium-B	Th B	²¹²Pb	earlier Th A ²¹⁶Po
Thorium-C	Th C	²¹²Bi
Thorium-C'	Th C'	²¹²Po	earlier Th C ²¹²Bi
Thorium-C''	Th C''	²⁰⁸Tl
Thorium-D	Th D	²⁰⁸Pb

Historical names of Thorium Isotopes

Name & Symbol (hist. and modern) First described Notes

Uranium X₁ U X₁ ²³⁴Th 1913 Kasimir Fajans & O.H. Göhring

Uranium Y U Y ²³¹Th 1911 Antonoff

Ionium Io ²³⁰Th 1908 Bertram B. Boltwood Boltwood separated a substance from Uranium minerals which he has called Ionium and described by Boltwood as having chemical properties very similar to those of Thorium.

Radiothorium RdTh ²²⁸Th 1905 Otto Hahn Hahn suggested the names Thorium 1, Thorium 2, and Thorium 3 for Mesothorium 1, Mesothorium 2, and Radiothorium respectively, but his suggestion was not followed

Radioactinium Rd Ac ²²⁷Th 1906 Otto Hahn

TEYAN
THORIUM, a very rare metal,
Is a gray powder with metallic lustre
Which, heated in Air, burns with great splendour,
Producing Thoria, snow-white whilst hot,
Yellow when cold. Thorium does not exist native,
But combined with Silica in Thorite
Found in Norway,and in min'ral Monascite.