Chapter 20.4, Problem 1PE

Interpretation Introduction

Interpretation:

The number of unpaired electrons in ${\left[\text{Mn}{\left({\text{H}}_{\text{2}}\text{O}\right)}_{\text{6}}\right]}^{\text{2+}}$ has to be determined. Provided that ${\text{H}}_{\text{2}}\text{O}$ is a weak field ligand.

Concept Introduction:

Strong field ligands:

• Gives larger splitting.
• So, $\text{splitting}\text{energy}{\text{Δ}}_{\text{o}}$ will be large.
• As a consequence electrons do not get transmitted to the higher energy level due to the large energy gap in between. So, remains paired up in the lower energy level.
• Thus, results in low-spin complexes.

Weak field ligands:

• Gives smaller splitting.
• So, $\text{splitting}\text{energy}{\text{Δ}}_{\text{o}}$ will be small.
• As a consequence electrons will easily get transmitted to the higher energy level due to the small energy gap in between. So, remains unpaired by occupying the higher energy level.
• Thus, results in high-spin complexes.

Ligand field splitting:

When ligands approach the central metal atom then the field strength of the ligand splits the outermost valence d orbitals of the central metal atom into two set of orbitals such as ${\text{t}}_{\text{2g}}$ and ${\text{e}}_{\text{g}}$ orbitals. The energy gap between two set of ${\text{t}}_{\text{2g}}$ and ${\text{e}}_{\text{g}}$ orbitals will be more or less based on the extent of splitting which in turn is based on the strength of the ligands. This phenomenon is known as Ligand field splitting.

The following diagram shows the splitting in the octahedral complexes:

Splitting energy is the energy between ${\text{t}}_{\text{2g}}$ and ${\text{e}}_{\text{g}}$ orbitals. The splitting energy distinguishes the energy of ${\text{t}}_{\text{2g}}$ and ${\text{e}}_{\text{g}}$ orbitals. ${\text{t}}_{\text{2g}}$ orbitals are the lower energy orbitals whereas ${\text{e}}_{\text{g}}$ orbitals are the higher energy orbitals. Splitting energy is represented as ${\text{Δ}}_{\text{o}}$ .

Pairing energy is the energy required to pair up electrons in an orbital. It is represented as $\Pi$.