Which of the following catio can not give bead test?

Options

A. `Cr^(3+)`
B. `Co^(2+)`
C. `Ag^(+)`
D. `Mn^(2+)`

Explanation

To determine which of the given cations cannot give a borax bead test, we need to understand the borax bead test and the nature of the cations provided.

### Step-by-Step Solution:

1. **Understanding the Borax Bead Test**:
- The borax bead test is a qualitative analysis method used to identify certain metal ions based on the color of the bead formed when the metal salt is heated with borax (sodium tetraborate).
- The test is particularly useful for identifying metal ions that form colored compounds.

2. **Identifying the Cations**:
- The cations provided in the question are:
- Cr³⁺ (Chromium)
- Co²⁺ (Cobalt)
- Ag⁺ (Silver)
- Mn²⁺ (Manganese)

3. **Analyzing Each Cation**:
- **Cr³⁺**: Forms a green bead when heated with borax.
- **Co²⁺**: Forms a blue bead when heated with borax.
- **Ag⁺**: Forms AgBO₂, which is a white or colorless compound when heated with borax.
- **Mn²⁺**: Forms a pink bead when heated with borax.

4. **Conclusion**:
- Among the given cations, Ag⁺ does not produce a colored bead; instead, it produces a white or colorless compound (AgBO₂). Therefore, it cannot give a borax bead test.

Thus, the cation that cannot give a borax bead test is **Ag⁺**.

### Final Answer:
**Ag⁺ (Silver ion)** cannot give the borax bead test.