When $[\text{Cr}(\text{NH}_3)_6]\text{Cl}_3$ dissolves in water, the three chloride ions present outside the coordination sphere ionise completely:

This yields $1$ complex cation $[\text{Cr}(\text{NH}_3)_6]^{3+}$ and $3$ chloride anions $\text{Cl}^-$, giving a total of $1 + 3 = 4$ ions.

In $[\text{Co}(\text{en})_3]_2(\text{SO}_4)_3$:

• Ethane-1,2-diamine ($\text{H}_2\text{NCH}_2\text{CH}_2\text{NH}_2$, abbreviated as en) is a neutral bidentate ligand (charge $= 0$).
• Sulphate ion ($\text{SO}_4^{2-}$) has a charge of $-2$.

Let the oxidation state of cobalt be $x$:

IUPAC naming of $[\text{Co}(\text{NH}_3)_5\text{Cl}]\text{Cl}_2$:

• In the coordination entity, ligands are named in alphabetical order: 'ammine' precedes 'chlorido' $\rightarrow$ pentaamminechlorido.
• The coordination sphere is cationic ($[\text{Co}(\text{NH}_3)_5\text{Cl}]^{2+}$), so the central metal retains its regular English name 'cobalt' (not cobaltate).
• Oxidation state of cobalt: $x + 5(0) + (-1) = +2 \implies x = +3$, written in Roman numerals as (III).
• The ionizable anion is named as 'chloride' (the numerical prefix 'di-' is never used for counter ions).