Question

The formula for the compound tris ( ethane -1, 2 -diamine ) cobalt ( Ill ) sulphate is :

{A.{\text{ }}\left[ {Co{\text{ }}{{\left( {en} \right)}_3}} \right]{\text{ }}S{O_4}} \\\ {B.{\text{ }}\left[ {Co{\text{ }}{{\left( {SO} \right)}_4}{{\left( {en} \right)}_3}} \right]} \\\ {C.{\text{ }}\left[ {Co{\text{ }}{{\left( {en} \right)}_3}} \right]{\text{ }}{{\left( {S{O_4}} \right)}_2}} \\\ {D.{\text{ }}{{\left[ {Co{\text{ }}{{\left( {en} \right)}_3}} \right]}_2}{{\left( {S{0_4}} \right)}_3}} \end{array}$$

Answer 1

IUPAC nomenclature is used to make an international standard of naming molecules to help in communication . According to the IUPAC nomenclature, every coordination compound can be named unique and can be given a unique structure. A certain set of rules must be followed to name the compound.
Complete step by step answer:
According to the IUPAC nomenclature rule, for naming at first name the ligands with their number. After that name the metal mentioning the oxidation state in bracket.For naming ligands, ionic ligand like chloride is chloride, sulfate is sulfato, nitrate is nitrato, hydride is hydrido etc. for neutral ligands like ammonia is ammine, water is aqua, carbon monoxide is carbonyl etc.
Now to mention the number numerical prefixes are used,

Number	Prefix	Number	Prefix
1	Mono	5	Penta
2	Di	6	hexa
3	Tri	7	hepta
4	Tera	8	octa

For metals, if the overall complex part of the compound is negatively charged then the name of the metal is ended with ‘ate’. For example

Metal	Name
Iron	Ferrate
Copper	Cuprate
Lead	Plumbate
Gold	Aurate

But for neutral or positive charged complexes the name of the metal is the same as their name.
For example, the name, tris ( ethane -1, 2 -diamine ) cobalt ( Ill ) sulphate.
The formula is, $\;{\left[ {Co{\text{ }}{{\left( {en} \right)}_3}} \right]_2}{\left( {S{0_4}} \right)_3}$
In this complex the oxidation number of cobalt is +3

So, the correct option is D.

Note:
According to the IUPAC nomenclature rule, for naming at first name the ligands with their number. After that name the metal mentioning the oxidation state in brackets. if in the complex the ligand name has some prefix like di, tri, hexa, then to mention their number prefixes like bis for two, tris for three, tetrakis etc. are used. For bridging ligands prefix like $\;\mu$ is used.