Question

Which one of following complex has the highest magnitude of crystal field splitting energy $\left({\Delta }_o\right)$ ?

• A. ${\left[Co{\left(H_{2}O\right)}_6\right]}^{3+}$
• B. ${\left[Co{\left(N{H}_3\right)}_6\right]}^{3+}$
• C. ${\left[Co{\left(C_2{O}_4\right)}_3\right]}^{3-}$
• D. ${\left[Co{F}_6\right]}^{3-}$

Answer 1

Answer: (B)

The crystal field splitting, i.e. ${\Delta }_o$, depends upon the field produced by the ligand and charge on the metal ion.

So, ligands can be arranged in a series in the order of increasing field strength. This series is known as spectrochemical series.

e.g., $I^{\ominus }<B{r}^{\ominus }<SC{N}^{\ominus }<C{l}^{\ominus }<F^{\ominus }<O{H}^{\ominus }<C_2{O}_4^{2-}$

$<H_{2}O<NC{S}^{\ominus }<EDT{A}^{4-}<N{H}_3<en<C{N}^{\ominus }<CO\because$

Among the given options, ligand $\left(N{H}_3\right)$ has highest magnetic field therefore, it has maximum value for ${\Delta }_o$.