What makes these chemical compound names incorrect?

Question

I'm a Chemistry II student and soon being tested on compound names; I bombed the quiz where it was asking for which compound names were wrong out of a list. These are the incorrect ones; can you explain why they are incorrect so I can know what to look for?

I have to put spaces between the components of the compound names to prevent Yahoo! from cutting them off. I put an _ where there's an actual space in the name given.

1. [Cr(NH3)3(OH)3] = triammine trihydroxo chromate(III)

2. [Mn(CN)5]^2- = pentacyano maganate(II) _ ion

3. [CoClBr(NH3)4]I = tetraammine bromo chloro cobalt(II) _ iodide

4. [Cr(NH3)3(OH)3] = triammine trihydroxo chromium(IV)

5. [Co(en)3]3(SO4)2 = tris(ethylenediamine) cobalt(III) _ sulfate

6. Na2[Sn(CN)5(OH)] = sodium _ hydroxo pentacyano stannate(IV)

Answer 1

1. The "chromate" at the end is incorrect since the species is not negatively charged. The name is triammine trihydroxo chromium(III).

2. The total charge of the ion is -2 and each cyanide contributes -1 (-5 total); hence the manganese atom is in the III oxidation state. The name is pentacyano manganate(III) ion.

3. The charge on the complex ion is +1 (because of the iodide counter ion). The Cl and Br each contribute -1 (whereas NH3 is neutral). Therefore, the charge on cobalt is +3. The name is tetrammine bromo chloro cobalt(III) iodide. (Note that we don't write tetraammine, we write tetrammine - as far as I know.)

4. The species is neutral; each OH contributes -1, and NH3 is neutral. Hence, the charge on Cr is +3. The name is triammine trihydroxo chromium(III).

5. The tris(ethylenediamine) cobalt(III) ion would be [Co(en)3]3+. Therefore, the formula of the compound is wrong: it should be [Co(en)3]2(SO4)3.

6. cyano comes before hydroxo lexicographically. The name should be sodium pentacyano hydroxo stannate(IV).