Crossword clues for thorium
thorium
The Collaborative International Dictionary
Thorium \Tho"ri*um\, n. [NL. See Thorite.] (Chem.) A metallic element found in certain rare minerals, as thorite, pyrochlore, monazite, etc., and isolated as an infusible gray metallic powder which burns in the air and forms thoria; -- formerly called also thorinum. Symbol Th. Atomic weight 232.0.
Douglas Harper's Etymology Dictionary
rare metallic element, 1832, Modern Latin, named by its discoverer, Swedish chemist Jöns Jakob Berzelius (1779-1848) from thorite (silicate of thorium), the name of a mineral found in Norway from which it was extracted (which Berzelius also had named, as thoria, in 1828), and named in honor of the Scandinavian god Thor. With chemical ending -ium.
Wiktionary
n. A chemical element (''symbol'' Th) with atomic number 90.
WordNet
n. a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands [syn: Th, atomic number 90]
Wikipedia
Thorium is a chemical element with symbol Th and atomic number 90. A radioactive actinide metal, thorium is one of only two significantly radioactive elements that still occur naturally in large quantities as a primordial element (the other being uranium). It was discovered in 1829 by the Norwegian priest and amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, the Norse god of thunder.
A thorium atom has 90 protons and therefore 90 electrons, of which four are valence electrons. Thorium metal is silvery and tarnishes black when exposed to air, forming the dioxide. Thorium is weakly radioactive: all its known isotopes are unstable. Thorium-232 (Th), which has 142 neutrons, is the most stable isotope of thorium and accounts for nearly all natural thorium, with six other natural isotopes occurring only as trace radioisotopes. Thorium has the longest half-life of all the significantly radioactive elements, 14.05 billion years; it decays very slowly through alpha decay to radium-228 (Ra), starting a decay chain named the thorium series that ends at stable lead-208 (Pb). Thorium is estimated to be about three to four times more abundant than uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare earth metals.
Thorium was once commonly used as the light source in gas mantles and as an alloying material, but these applications have declined due to concerns about its radioactivity. Thorium is still widely used as an alloying element in TIG welding electrodes (at a rate of 1%–2% mix with tungsten). It remains popular as a material in high-end optics and scientific instrumentation; thorium and uranium are the only significantly radioactive elements with major commercial applications that do not rely on their radioactivity. Thorium is predicted to be able to replace uranium as nuclear fuel in nuclear reactors, but only a few thorium reactors have yet been completed.
Usage examples of "thorium".
In a moment he stood aside and Koa lifted out a perfect ring of thorium.
Some of these were easily converted into fissionable uranium 235, and thorium 232 itself was an enormously valuable breeder material for an atomic pile.
The intermediate elements referred to in this radioactive decay chain are lead (symbol Pb, element 82), polonium (Po, element 84), astatine (At, element 85), francium (Fr, element 87), radium (Ra, element 88), actinium (Ac, element 89), thorium (Th, element 90), protoactinium (Pa, element 91), uranium (U, element 92), neptunium (Np, element 93), and americium (Am, element 95).
They have, it is to be presumed, been setting up nuclear intensifiers in places where the soil is rich in uranium or thorium.
Thus were found the mesothorium now used by physicians and manufactured industrially, radio thorium, ionium, protoactinium, radio-lead, and other substances.
It is a typical organic compound, one of the metal radical type, and contains one atom of thorium.
But when the Mole materialized, the phosphoric acid dissolved off the remaining thin plating of thorium from the screws.
When I was a child, it never dawned on me that someone supposedly being starved and beaten in a thorium mine shouldn't have all those luscious curves.
It was now necessary to jack the rocket around until the tubes pointed away from the cabin, so that radiations, after the thorium was in place, would go harmlessly out across the crater of the Doomsday Bomb and, also, so that the rocket would be in position for a captive test run with the exhaust directed away from the cabin.
If he impregnated a cylindrical fabric with thorium nitrate, to which was added a small percentage of cerium nitrate, he got a brilliant white glow.
And it turns out, quite clearly--I will show you all the necessary data at any time you wish--that uranium and thorium collect in Earths crust and upper mantle in concentrations of up to a thousand times as high as in any other habitable world.
But some isotopes of uranium and thorium have little beta, with some alpha and gamma, so Baxter concluded we had powdered uranium ore.