According to crystal field theory, the correct order of ligands...

According to crystal field theory, the correct order of ligands with respect to their decreasing order of field strength is

Options

A $\text{Cl}^->\text{NH}_3>\text{H}_2\text{O}>\text{CO}$
B $\text{CO}>\text{NH}_3>\text{H}_2\text{O}>\text{Cl}^-$
C $\text{CO}>\text{H}_2\text{O}>\text{NH}_3>\text{Cl}^-$
D $\text{Cl}^->\text{H}_2\text{O}>\text{NH}_3>\text{CO}$

Correct answer

B. $\text{CO}>\text{NH}_3>\text{H}_2\text{O}>\text{Cl}^-$

Step-by-step solution

According to the spectrochemical series, the arrangement of ligands in the increasing order of their crystal field splitting energy (CFSE) or field strength is:

\text{I}^- < \text{Br}^- < \text{SCN}^- < \text{Cl}^- < \text{S}^{2-} < \text{F}^- < \text{OH}^- < \text{C}_2\text{O}_4^{2-} < \text{H}_2\text{O} < \text{NCS}^- < \text{edta}^{4-} < \text{NH}_3 < \text{en} < \text{CN}^- < \text{CO}

From the given ligands, the decreasing order of field strength is:

\text{CO} > \text{NH}_3 > \text{H}_2\text{O} > \text{Cl}^-

Answer:

\text{CO}>\text{NH}_3>\text{H}_2\text{O}>\text{Cl}^-

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