Radioctive dating against evolution
In the beginning of period 7, from francium to thorium, the melting points of the elements increase (as in other periods), because the number of delocalised electrons each atom contributes increases from one in francium to four in thorium, leading to greater attraction between these electrons and the metal ions as their charge increases from one to four.After thorium, there is a new downward trend in melting points from thorium to plutonium.U) that have half-lives measured in billions of years; its half-life is 14.05 billion years, about three times the age of the earth, and slightly longer than the age of the universe.
This chain of consecutive alpha and beta decays begins with the decay of Th also very occasionally undergoes spontaneous fission rather than alpha decay, and has left evidence in doing so in its minerals (as trapped xenon gas formed as a fission product), but the partial half-life of this process is very large at over 10Np: the last of these is long extinct in nature due to its short half-life (2.14 million years), but is continually produced in minute traces from neutron capture in uranium ores.
Thorium is a chemical element with symbol Th and atomic number 90.
Thorium metal is silvery and tarnishes black when it is exposed to air, forming the dioxide; it is moderately hard, malleable, and has a high melting point.
The most stable isotope of thorium, It is estimated to be over three 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 discovered in 1829 by the Norwegian amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, the Norse god of thunder.