Consider the different types of isomerism in coordination compounds, such as linkage isomerism, ionization isomerism, geometrical isomerism, and optical isomerism.
\(\left[ Co \left( H _2 O \right)_6\right]^{3+}\)
\(\left[ Co \left( NH _3\right)_5 Cl \right]^{+}\)
\(\left[ Co \left( NH _3\right)_5 NO _2\right]^{2+}\)
\(\left[ Co \left( NH _3\right)_5 Cl \right]^{2+}\)
Step 1: Analyze the Complexes for Isomerism
We are looking for a complex cation that exhibits two isomers. Let’s analyze each option:
\([ \text{Co}(\text{H}_2\text{O})_6 ]^{3+}\):
This complex has only one possible structure, as all ligands are the same (\(\text{H}_2\text{O}\)). So, it does not have isomers.
\([ \text{Co}(\text{NH}_3)_5\text{Cl} ]^{2+}\):
This complex can only exhibit ionization isomerism if another counter ion is present within the complex to exchange positions with the \(\text{Cl}\) ligand. With only one \(\text{Cl}\), there’s no possibility of isomerism here.
\([ \text{Co}(\text{NH}_3)_5\text{NO}_2 ]^{2+}\):
This complex can exhibit linkage isomerism because the \(\text{NO}_2\) ligand can coordinate to the metal ion through either the nitrogen atom (nitro isomer) or the oxygen atom (nitrito isomer). Thus, it has two isomers.
\([ \text{Co}(\text{NH}_3)_5\text{Cl} ]^{+}\):
Same explanation as (2), no isomerism is possible
Conclusion
The correct option is (3): \([ \text{Co}(\text{NH}_3)_5\text{NO}_2 ]^{2+}\), which exhibits two isomers (nitro and nitrito isomers).
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)

Cobalt chloride when dissolved in water forms pink colored complex $X$ which has octahedral geometry. This solution on treating with cone $HCl$ forms deep blue complex, $\underline{Y}$ which has a $\underline{Z}$ geometry $X, Y$ and $Z$, respectively, are
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)
A black body is at a temperature of 2880 K. The energy of radiation emitted by this body with wavelength between 499 nm and 500 nm is U1, between 999 nm and 1000 nm is U2 and between 1499 nm and 1500 nm is U3. The Wien's constant, b = 2.88×106 nm-K. Then,
A coordination compound holds a central metal atom or ion surrounded by various oppositely charged ions or neutral molecules. These molecules or ions are re-bonded to the metal atom or ion by a coordinate bond.
A coordination entity composes of a central metal atom or ion bonded to a fixed number of ions or molecules.
A molecule, ion, or group which is bonded to the metal atom or ion in a complex or coordination compound by a coordinate bond is commonly called a ligand. It may be either neutral, positively, or negatively charged.