Chapter 20, Problem 20.126CHP

Interpretation Introduction

Interpretation:

The reason for having different colours for ${\left[CoC{l}_4\right]}^{2-}$ and ${\left[Co{\left(H_{2}O\right)}_6\right]}^{2+}$ has to be determined and also has to identify the complex which has its absorption bands at longer wavelengths.

Concept introduction:

Coordination compounds: The compounds having coordination covalent bonds which form when metal ions react with polar molecules or anions

Visible region: The electromagnetic radiation in range of $400-700nm$ is regarded as visible region which is actually visible to human eyes.

Absorption spectrum: It is an electromagnetic spectrum where the radiation transmitted via substance shows bands as a result of absorbing intensity of radiation at specific wavelength.

$Spectrochemical$ Series: The list of ligands arranged in an ascending order of $\text{(Δ)}$(the splitting of d-orbitals in presence of various ligands).

$\begin{array}{l}\stackrel{{}^{{\text{I}}^{\text{-}}\text{<}{\text{Br}}^{\text{-}}\text{<}{\text{SCN}}^{\text{-}}\text{<}{\text{Cl}}^{\text{-}}\text{<}{\text{S}}^{\text{2-}}\text{<}{\text{F}}^{\text{-}}\text{<}{\text{OH}}^{\text{-}}\text{<}{\text{O}}^{\text{2-}}\text{<}{\text{H}}_{\text{2}}\text{O}\text{<}{\text{NCS}}^{\text{-}}\text{<}{\text{edta}}^{\text{4-}}\text{<}{\text{NH}}_{\text{3}}\text{< en}\text{<}{\text{NO}}^{\text{2-}}\text{<}{\text{CN}}^{\text{-}}\text{<}\text{CO}}}{\to }\\ {}_{{}^{{}^{\begin{array}{l}\text{weak-field}\text{increasing(Δ)}\text{strong-field}\\ \text{ligands}\text{ligands}\end{array}}}}\end{array}$

The strong field ligands lead to splitting to a higher extent than the weak field ligands and the wavelength of light absorbed depends on the energy gap that is produced by a particular ligand.