Name the complex ion [Co(NH3)6]3+ and determine the oxidation and coordination numbers of cobalt.

The ligand is ammonia ($NH_3$), which is named ammine in coordination compounds. There are 6 ammine ligands. The central metal is cobalt (Co).

Let the oxidation state of cobalt be $x$. The ammonia ligand is neutral, so its charge is 0. The overall charge of the complex ion is $+3$.

The oxidation state of cobalt is +3, denoted as (III).

The name starts with the number and name of the ligand, followed by the metal name and its oxidation state in Roman numerals, and finally "ion" because it's a charged species.
The name is hexaamminecobalt(III) ion.

a) (ii)

As calculated in Step 2 above, the oxidation number of cobalt is +3.

The coordination number is the number of ligand atoms directly bonded to the central metal ion. In $[Co(NH_3)_6]^{3+}$, there are 6 $NH_3$ ligands, and each $NH_3$ is a monodentate ligand.
Therefore, the coordination number is 6.

a) (i) Name the complex ion:

a) (ii)
Oxidation number: $\boxed{+3}$
Coordination number: $\boxed{6}$