Question

Using the valence bond theory, predict the geometry and the magnetic behaviour of ${[Co{F_6}]^{3 - }}$. [Atomic number of $Co$ is 27].

Answer 1

Hint: The compounds which form complex compounds are found to have the property of directional bonds. Along with the directional bonds and the complex arrangement of the ions in the respective coordination spheres the coordination compounds also have characteristic features of magnetic and optical properties.

Complete step by step answer:
The valence bond theory explains the properties of the complex compounds that we are unable to be explained by the previous theories. The valence bond theory is based on the ideas of bond enthalpy and the overlapping of the atomic orbitals. The central atom of the complex ${[Co{F_6}]^{3 - }}$ is the atom $Co$ with the atomic number 27. So, the atomic configuration can be written as $[Ar]3{d^7}4{s^2}$ .
In the complex ${[Co{F_6}]^{3 - }}$ the ion on the central atom can be calculated as

x + ( - 6) = - 3

$\Rightarrow x = + 3$

Where $x$ is the effective charge on the central atom. So, the atomic configuration of $C{o^{ + 3}}$ can be written as $[Ar]3{d^6}$The vacant one 4s, three 4p and two 4d orbitals which are free, combine and overlap to form the orbital of $s{p^3}{d^2}$ to accommodate the six electron pair of fluorine. Since the compound contains the weak ligand so the electrons are not paired up in the d orbital and 4 electrons remain unpaired in the 3d orbital.

Hence the compound is said to be paramagnetic.So, the $s{p^3}{d^2}$ hybridization has the octahedral geometry .

Note: When two atoms combine to form a molecule a certain amount of energy is released upon the formation of the new molecule. This molecule resulting from such bonding is much lower in energy and stable than the individual atoms. The energy so released is called bond enthalpy.
During the formation of the bond, the orbitals of the atoms are so close that their orbitals undergo interpenetration. This forms the partial merging of the orbitals and thus formed the concept of overlapping of atomic orbitals.