Abegg’s rule :
An empirical rule, holding for a large number of elements, that
the sum of the maximum positive and negative valencies of an element equals eight.
In general, for a given chemical element (as sulfur) Abegg’s rule states that the sum of the absolute value of its negative valence (such as −2 for sulfur in H2S) and its positive valence of maximum value (as +6 for sulfur in H2SO4) is often equal to 8.
