Moseley’s rule

After Niels Bohr s proposal of the atomic model and the reinterpretation of the periodic system by Moseley s rule, the search for the missing elements received a new impetus and numerous were the attempts to fill the last gaps in the periodic table. Several rare earths were isolated and, by 1924, only five elements were still to be discovered numbers 43, 61, 75, 85, and 87. Four of those elements are the natural radio-elements 43, 61, 85, and 87 and, for this reason, they escaped the searches led by chemists who were missing the right tool to isolate or even produce them in observable quantities. This was not the case with rhenium (element 75), the last stable element to be discovered and also one of the less abundant in the earth s crust. 

The Periodic Table of the elements was set up in 1869 by Lothar Meyer and independently by D. Mendeleyev, in order to arrange the elements according to their chemical properties and to make clear the relationships between the elements. This table allowed valuable predictions to be made about unknown elements. With respect to the order of the elements according to their atomic numbers Moseley s rule proved to be very useful ... 

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