Which of the following is not chelating agent
(a) Thiosulphate
(b) Oxalato
(c ) Glycinato
(d) Ethylene diamine .

Options

A. Thiosulphato
B. Oxalato
C. Glycinato
D. Ethane-1, 2-diamine

Explanation

To determine which of the following is not a chelating agent, we need to analyze each option based on the definition of a chelating agent. A chelating agent is a multidentate ligand that can form multiple bonds with a metal ion, creating a ring-like structure known as a chelate.

### Step-by-Step Solution:

1. **Understand the Definition of Chelating Agents**:
- A chelating agent is a ligand that can attach to a metal ion at multiple sites, forming a stable ring structure.

2. **Analyze Each Option**:
- **Option (a) Thiosulphate (H2O3S)**:
- Thiosulphate has a formula of \( \text{S}_2\text{O}_3^{2-} \). It has only one sulfur atom that can donate electrons to a metal ion, making it a monodentate ligand. Therefore, it does not form a chelate.

- **Option (b) Oxalato (C2O4^{2-})**:
- Oxalato has two oxygen atoms that can donate electrons, making it a bidentate ligand. It can form a chelate with metal ions.

- **Option (c) Glycinato (C2H4N1O2^{-})**:
- Glycinato has both a nitrogen atom and an oxygen atom that can donate electrons, making it a bidentate ligand. It can also form a chelate with metal ions.

- **Option (d) Ethylene diamine (C2H8N2)**:
- Ethylene diamine has two nitrogen atoms that can donate electrons, making it a bidentate ligand as well. It can form chelates with metal ions.

3. **Conclusion**:
- From the analysis, we find that:
- Thiosulphate is a monodentate ligand and does not form chelates.
- Oxalato, Glycinato, and Ethylene diamine are all chelating agents.
- Therefore, the answer is **(a) Thiosulphate**.

### Final Answer:
**(a) Thiosulphate is not a chelating agent.**