Complex compounds that have the same molecular formula but have different structural/space arrangements of ligands around central metal atom/ion are called isomers, these are of two types namely structural and stereoisomers.
Q. Which of the following is different among structural isomers?

Options

A. Oxidation state
B. Co-ordination number
C. IUPAC name
D. None of these

Answer

To solve the question regarding the differences among structural isomers, we can follow these steps:

### Step 1: Understand the concept of isomers
Isomers are compounds that have the same molecular formula but different structural or spatial arrangements of atoms. They can be classified into two main types: structural isomers and stereoisomers.

**Hint:** Remember that structural isomers differ in how their atoms are connected, while stereoisomers differ in the spatial arrangement of their atoms.

### Step 2: Identify the types of structural isomers
Structural isomers can be further divided into several categories, including:
- Chain isomerism
- Position isomerism
- Functional group isomerism
- Linkage isomerism

**Hint:** Think about how the arrangement of ligands or functional groups can lead to different structural forms.

### Step 3: Analyze the options given in the question
The question provides four options regarding what could be different among structural isomers:
1. Oxidation state
2. Coordination number
3. IUPAC name
4. None of these

**Hint:** Consider how each of these properties might change or remain the same when comparing structural isomers.

### Step 4: Evaluate each option
- **Oxidation state:** In structural isomers, the oxidation state of the central metal ion often remains the same. For example, if you have a metal ion with a certain oxidation state in one isomer, it will typically have the same oxidation state in its structural isomer.

- **Coordination number:** The coordination number, which is the number of ligands attached to the central metal ion, also remains the same among structural isomers. For instance, if a complex has six ligands in one isomer, it will have six in all structural isomers.

- **IUPAC name:** The IUPAC name of structural isomers will differ due to the different arrangements of ligands. For example, if one isomer has a thiocyanate ligand (SCN) and another has an isothiocyanate ligand (NCS), their IUPAC names will reflect this difference.

- **None of these:** This option implies that none of the previous options differ, which is not correct since we have established that the IUPAC names differ.

**Hint:** Focus on the unique naming conventions in chemistry that ensure each compound has a distinct name based on its structure.

### Step 5: Conclusion
Based on the analysis, the correct answer is that the **IUPAC name** is different among structural isomers.

### Final Answer
**IUPAC name**