Genesis of the elements

Crookes, William. 1887. Genesis of the Elements. London Royal Institution. 

Some artificial elements (group c) have probably been produced in the course of the genesis of the elements and were present on the earth at the time of its formation. The age of the earth is estimated to be about 4.5 10 y. During this time elements of shorter half-life disappeared by nuclear transformations. After waiting for about 10 y, most of the artificial elements would have decayed again, and after a much longer time (about 10 y) the radioelements U and Th would also not exist any more on the earth in measurable amounts, with the consequence that the Periodic Table of the elements would end with element 83 (Bi = bismuth). 

Several radionuclides are continuously produced by the impact of cosmic radiation, and the main representatives of this group are C, Be, Be and H. Radionuclides present in nature in extremely low concentrations, such as Pu and its decay products or products of spontaneous fission of U and Th, are not considered in this list. Radionuclides existing from the beginning, i.e. since the genesis of the elements, are called primordial radionuclides. They comprise the radionuclides of group (2) and Th and Pu. 

Lead has four stable isotopes, Pb, Pb, Pb and 2 Pb. The stability of " Pb has been debated, but the half-life is >10 y and, with respect to the age of the earth and the universe, Pb can be considered to be stable. In the course of the genesis of the elements certain amounts of the above-mentioned four stable isotopes of Pb have been formed (primordial Pb). Additional amounts of Pb, Pb and Pb (radiogenic Pb) have been produced by the decay of and Th, respectively. 

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