Using VBT, explain the geometry and magnetic property of `[CO(NH_(3))_(6)]^(+3)`.

Explanation

In `[Co(NH_(3))_(6)]^(3+)` the cobalt ion is in `+3` oxidation state and has the electronic configuration.
`[Ar]3d^(6)4s^(0)`
Orbitals of cobalt `Co^(3+)` ion is represented as

When strong ligand, `NH_(3)` is approaching towards central metal ion, rearrangement of electrons takes place against the Hund.s rule.

Tow d orbitals, one s orbital and three p orbitals undergo hybridization to form six `d^(2)sp^(3)` hybridized orbitals of cobalt pointing towards the six corners of an octahedron. Six d.sp hybrid orbitals

These six hybridised orbitals Cot overlaps with orbitals of six ammonia ligands and six pairs of electrons donated by six ammonia ligands to form six coordinate bonds.

Six `d^(2)sp^(2)` hybrid orbitals with six pairs of electrons of `NH_(3)` ligands Thus the complex has octahedral geometry and is dia-magnetic because of the absence of unpaired electron in the formation of this complex, since the inner d orbital (3d) is used in hybridisation, the complex `[Co(NH_(3))_(6)]^(3+)` is called an inner orbital complex (or) Low spin complex (or) spin paired complex.