Chapter 22, Problem 2SEPP

Interpretation Introduction

Interpretation:

Thecolors of the given complex compounds are to be determined.

Concept introduction:

Sunlight comprises all thecolors. The objects reflecting all these colors appear white and the objects absorbing all these colors appear black. Any object that absorbs all colors but reflects a particular color is said to possess that color.

The color in coordination compounds can be explained on the basis of crystal field splitting energy by using the expression below:

$\Delta E\text{(or simplyΔ)}=\text{h}\frac{\text{c}}{\text{λ}}$

Here, $\Delta E$ is the change in energy, $\text{c}$ is the speed of light, $\text{h}$ is Planck’s constant, and $\lambda$ is the wavelength of the photon.

The color of a complex compound is the same as the magnitude of the energy of a photon of visible light. The transition metal complex absorbs visible light, which causes the electron to jump from the lower-energy $d$-orbital to the higher-energy $d$-orbital. The complementary color produced (refer to figure 22.14 of the book) from the wavelengths after some wavelength from the white light is absorbed for the excitation of the electron.

Spectrochemical series: ${\text{I}}^{-}{\text{< Br}}^{-}{\text{< Cl}}^{-}{\text{< OH}}^{-}{\text{< F}}^{-}{\text{< H}}_2{\text{O < NH}}_3{\text{< en < CN}}^{-}\text{< CO}$

These ligands are arranged in order of increasing value of $\Delta E$.