[gsxrguru2]

(NH4)2-SO4 I'm thinking it is ammonium persulfate but when i google that, it shows that it should have 8 oxygens instead of the four. I realized that it is in fact ammonium sulfate, but from what i'm reading in my book, it seems that it should be persulfate. any help? Thanks!

[Borek]

Why do you think it is persulfate?

[gsxrguru2]

i was thinking that since its a polyatomic anion with 4 oxygens that it should start with per (root) and end in ate. although now that I'm looking closer at my notes, it appears that that applies to the 7A halogens. correct?

[AWK]

(NH4)2S2O8 is called ammonium persulfate

[Yggdrasil]

The system for naming oxyanions is far from optimal.  Basically, the most common of the series of oxyanions is given the -ate name.  So, for example, sulfate and phosphate are SO₄^2- and PO₄^3- while nitrate and chlorate are NO₃^- and ClO₃^-.  Then the naming system use the common oxidation state as a base and name the per_ate, -ite, and hypo_ite based on the oxidation state of the -ate species.

So, while many per_ates have four oxygens, this is not always the case.  Similarly, many -ate anions have three oxygens, but this is not a rule.

[gsxrguru2]

Thanks for clarifying things, even if its still clear as mud as they say. Joys of learning chemistry, right?

[Yggdrasil]

At least the nomenclature in chemistry makes more sense than the nomenclature in biology.

[agrobert]

^yea and we don't memorize three letter codes blatantly without knowing the structure