[Lii]

I'm just a little confused at the moment.

We had a very long lab where we were given unknowns and we had to find out what cations and anions we had in them using various qualitative methods.

My unknown was mostly black and gray crystals, but there were some white/colorless ones and just a few brownish crystals too.

I determined (and this has been confirmed) that I have Iron (iii), Lead (ii), Zinc, Iodine, and Nitrate.

However, what's confusing me is that when I looked up the possible combinations (PbI₂, Fe(NO₃)₃, etc.) none of them appear as black or gray crystals. So I'm kind of stuck about what to do next to figure out the compounds I have. Unless I misunderstood my professor, my elements should be in the form of compounds like that.

Any tips would be greatly appreciated!

[spirochete]

With transition metals and larger elements I'd guess the only 100% reliable way would be a quantitative treatment of molecular orbital theory.

Luckily you're dealing with a limited number of possible compounds so you can just look them up individually! Or use the experimental evidence. I didn't have time to read your post in that much detail.