The evaluation of mass number of elements from their electronic configurations

An attempt has been made to establish a simple rule by which one can calculate the value of the mass number of the stable isotope of an element with a fair degree of accuracy. The rule is expressed by the relation: X=2Z+number of d and f electrons, where X=mass number, Z=atomic or protonic number of the element in question. Some more relations are also obtained for ranges of atomic number. It is claimed that they give more accurate mass numbers. (M.G.B.)