it is written backward, meaning is "how much is seven plus one" anwser is "osem"
Means nothing. Even phonetically it does not sound as a meaningful expression.
There are two compounds ferrous sulfide and ferrous sulfate.
A single atom of sulphur combined to a metal . e.g. ZnS = Zinc sulphide. H2S = Hydrogen sulphide ( Bad eggs smell). To further clarify the nomenclature (naming system) ZnSO3 = zinc sulpite ; H2SO3 Sulp[hurous Acid ZnSO4 = zince sulphate ; H2SO4 Sulphuric Acid. NB #1 ; 'S' no oxygen #2 ; 'SO3' three oxygens #3 ; 'SO4' four oxygens. NNB Note the change of one letter to indicate the change of chemical formula.