Abegg's rule

noun

ˈä-ˌbegz-  -ˌbeks- 

: a rule in chemistry: for a given chemical element (as sulfur) the sum of the absolute value of its negative valence of maximum absolute value (as −2 for sulfur in H₂S) and its positive valence of maximum value (as +6 for sulfur in H₂SO₄) is often equal to 8