[mandyj]

I'm having trouble with naming these formula:

Al2(MnO4)3    ---> I got dialuminum permangante
Al2(N2O2)3    ---> aluminum dinitrogen dioxide?? I didn't think N2O2 could be a polyatomic ion

Hg2I2 --> mercury (II) diiodide
sodium peroxide --> Na O (not sure what to do for "per" oxide)

[Yggdrasil]

First, remember that you don't need numerical prefixes (e.g. di, tri, tetra, etc.) when naming ionic compounds.  So, Al₂(MnO₄)₃ is aluminum permanganate manganate. (note: since the aluminum ion has a charge of +3, this means that the anion has a -2 charge.  Therfore, the anion is manganate [MnO₄^2-], not permanganate [MnO₄^-])

These formulas are tricky since they involve very weird ions.  For example, mercury has two common oxidation states.  Mercury (II) is Hg²⁺, but mercury (I) is Hg₂²⁺.  I don't know why the mercury (I) ions form a dimer, but that's how it behaves.  Similarly, oxygen normally will form oxide ions (O^2-), but it can also form peroxide ions (O₂^-).

Unfortunately, I don't know the name of the N₂O₂^- ion either.

[edit: it's actually aluminum manganate, not aluminum permanganate]

[ellis1101]

wouldn't N2O2 be dinitrogen peroxide? . and I'm pretty sure you're right about the permangate thing, because it has 1 more oxygen than mangate (MnO3)
So they should really be
Aluminum permangate
Aluminum dinitrogen peroxide
and
Sodium peroxide is Na2O2
and I don't know what the other guy is talking about, actually, O2 and Hg2 don't have charges... @_@

[agrobert]

O2 and Hg2 don't have charges

Oxygen does not have a charge but it can in inorganic complexes like Yggdrasil stated.  Mercury does have a charge depending on whether it is Hg(1) or Hg(II), follow Yggdrasil post.

Al₂(MnO₄)₃ aluminum manganate

Sodium peroxide Na₂O₂

Hg₂I₂ mercury (II) iodide

As long as you indicate the oxidation state of the transition metal you don't need numerical prefixes if the ligand is homoleptic-(the only type of ligand in the complex).