Identify the species in which the metal atom is in +6 oxidation state.

Options

A. `MnO_4^(-)`
B. `[Cr(CN)_6]^(3-)`
C. `[NiF_6]^(2-)`
D. `CrO_2Cl_2`

Explanation

To identify the species in which the metal atom is in +6 oxidation state, we will analyze each given compound step by step.

### Step-by-Step Solution:

1. **Analyze MnO4⁻ (Permanganate Ion)**:
- Let the oxidation state of Mn be \( x \).
- The oxidation state of oxygen (O) is -2.
- The formula for the permanganate ion is:
\[ x + 4(-2) = -1 \]
- Simplifying this:
\[ x - 8 = -1 \implies x = +7 \]
- Therefore, Mn is in the +7 oxidation state.

2. **Analyze Cr(CN)6³⁻ (Hexacyanocobaltate(III) Ion)**:
- Let the oxidation state of Cr be \( x \).
- The oxidation state of cyanide (CN) is -1.
- The formula for the hexacyanocobaltate ion is:
\[ x + 6(-1) = -3 \]
- Simplifying this:
\[ x - 6 = -3 \implies x = +3 \]
- Therefore, Cr is in the +3 oxidation state.

3. **Analyze NiF6²⁻ (Hexafluoronickelate(II) Ion)**:
- Let the oxidation state of Ni be \( x \).
- The oxidation state of fluorine (F) is -1.
- The formula for the hexafluoronickelate ion is:
\[ x + 6(-1) = -2 \]
- Simplifying this:
\[ x - 6 = -2 \implies x = +4 \]
- Therefore, Ni is in the +4 oxidation state.

4. **Analyze CrO2Cl2 (Dichromyl Chloride)**:
- Let the oxidation state of Cr be \( x \).
- The oxidation state of oxygen (O) is -2 and chlorine (Cl) is -1.
- The formula for dichromyl chloride is:
\[ x + 2(-2) + 2(-1) = 0 \]
- Simplifying this:
\[ x - 4 - 2 = 0 \implies x - 6 = 0 \implies x = +6 \]
- Therefore, Cr is in the +6 oxidation state.

### Conclusion:
The species in which the metal atom is in +6 oxidation state is **CrO2Cl2** (Dichromyl Chloride), where chromium (Cr) has a +6 oxidation state.