Question

IUPAC name for ${[Co{(N{H_3})_6}]^{2 + }}$ is:
(A) Hexammoniacobaltate(II) ion
(B) Hexaamminecobaltate(II) ion
(C) Hexammoniacobalt(II) ion
(D) Hexaamminecobalt(II) ion

Answer 1

Here the complex part of the compound is an cation.so we will follow the cation rules to find the IUPAC name of the compound. And the oxidation number of the central metal atom is decided by the balance of charge.

Complete step by step solution:
First of all let us talk about the complex compound and the oxidation number of an element.
Complex compound: These are substances in which the central metal atom is surrounded by non-metal atoms or groups of atoms (known as ligands). They are joined together by chemical bonds.
Oxidation number of an element: It is defined as the total number of electrons that an atom accepts or loses in order to make a chemical bond which results in the formation of a chemical compound. If an element accepts electrons then oxidation number will be negative and if element donates electron then its oxidation number will be positive.
Here in the question we are given with the compound ${[Co{(N{H_3})_6}]^{2 + }}$ . Here we can see that the cobalt atom is surrounded by six amine atoms. So it is a complex compound.
And the rule for the IUPAC nomenclature of cation complex is as follows:
Write the name of the ligand (i.e. the atoms or group of atoms which are attached to the central metal atom) indicating the number of molecules/ atoms such as di, tri, etc.
And then write the name of the central metal atom and at last write the oxidation number of the central metal atom in the brackets.
Here the oxidation number of cobalt is $2$ because the cation has charge $+ 2$ and the charge on each amine atom is $0$ . So the charge on the cobalt is $+ 2$ .
So the IUPAC name of the compound ${[Co{(N{H_3})_6}]^{2 + }}$ will be as: Hexaamminecobalt(II) ion.
Hence option D is correct.

Note:
If a compound has net charge either positive or negative then the sum of all charges in the compound will be equal to that net charge on the compound. By using this concept we can calculate the oxidation number of elements in charged species.