Which one of the following ions does not give borax bead test :

Options

A. `Cr^(3+)`
B. `Cu^(3+)`
C. `Mn^(2+)`
D. `Zn^(2+)`

Answer

To determine which ion does not give a borax bead test, we need to understand the borax bead test and the behavior of different ions during this test.

### Step-by-Step Solution:

1. **Understand 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 is heated with borax (sodium borate). Transition metals typically give colored beads due to the formation of colored metaborates.

2. **Identify the Ions in Question**:
The ions mentioned in the question are:
- Copper (Cu²⁺)
- Chromium (Cr³⁺)
- Manganese (Mn²⁺)
- Zinc (Zn²⁺)

3. **Analyze Each Ion**:
- **Copper (Cu²⁺)**: When heated with borax, copper forms a blue-colored metaborate.
- **Chromium (Cr³⁺)**: Chromium gives a green-colored metaborate when heated with borax.
- **Manganese (Mn²⁺)**: Manganese produces a pink-colored metaborate upon heating.
- **Zinc (Zn²⁺)**: Zinc does not produce a colored metaborate; instead, it forms a colorless compound.

4. **Conclusion**:
Since the borax bead test is characterized by the formation of colored compounds, and Zinc (Zn²⁺) does not produce any color (it is colorless), it does not give a borax bead test.

### Final Answer:
**Zinc (Zn²⁺) does not give the borax bead test.**