# Why hydrogen disulfide and not hydrogen persulfide?

Recently, I was checking on this question and I was thinking of the name of the compound $\ce{FeS2}$. Later I checked the name in the answer to be iron disulfide. I found the following statement in the comments section:

Persulphide? Disulphide is ok here but per- not really.

The answerer actually named $\ce{FeS2}$ to be iron persulfide but later changed to iron disulfide after responding to the comment.

I checked the google and found the wikipedia article of marcasite and referred its name to be iron(II) disulfide. But why? Why not iron persulfide? It contains the $\ce{S2^2-}$ ion which is named disulfide anion. Why not persulfide anion (as per analogy to peroxide anion $\ce{O2^2-}$)?

In a group, compound names are named similarly to follow a certain fashion/trend. For e.g. methane, silane, germane (group 14). So, why $\ce{H2O2}$ is hydrogen peroxide and $\ce{H2S2}$ is hydrogen disulfide? Why it is not named hydrogen persulfide by analogy?

• – DHMO Oct 29 '16 at 14:58
• @DHMO, So, why hydrogen dioxide is not the other name of hydrogen peroxide? – Nilay Ghosh Oct 29 '16 at 15:03
• @DHMO, and so, if it is hydrogen persulfide, so why not iron persulfide? – Nilay Ghosh Oct 29 '16 at 15:05
• Hydrogen peroxide can be alternatively called dihydrogen dioxide (note the prefix -di). As such, $\ce{FeS_2}$ could be called either iron(II) persulfde or iron(II) disulfide. Structurally speaking, though, in both cases the per-option is more appropriate. – Linear Christmas Oct 29 '16 at 18:12
• @LinearChristmas, would you consider converting your comment into answer? – Nilay Ghosh May 11 '17 at 12:00