Among the following identify the species with an atom in `+6` oxidation state.

Options

A. `MnO_(4)^(-)`
B. `Cr(CN)_(6)^(3-)`
C. `NiF_(6)^(2-)`
D. `CrO_(2)Cl_(2)`

Explanation

To determine which species has an atom in the +6 oxidation state, we will analyze each given compound step by step.

### Step-by-Step Solution:

1. **Identify the Compounds**: We need to analyze the oxidation states of the elements in the given compounds. The compounds mentioned are:
- \( \text{Cr}_2\text{O}_7^{2-} \)
- \( \text{Cr(CN)}_6^{3-} \)
- \( \text{NiF}_6^{2-} \)
- \( \text{CrO}_2\text{Cl}_2 \)

2. **Calculate the Oxidation State for Each Compound**:
- **For \( \text{Cr}_2\text{O}_7^{2-} \)**:
- Let the oxidation state of Cr be \( x \).
- The oxidation state of O is -2.
- The equation becomes:
\[ 2x + 7(-2) = -2 \]
\[ 2x - 14 = -2 \implies 2x = 12 \implies x = +6 \]
- So, Cr in \( \text{Cr}_2\text{O}_7^{2-} \) is +6.

- **For \( \text{Cr(CN)}_6^{3-} \)**:
- The oxidation state of CN is -1.
- Let the oxidation state of Cr be \( x \).
- The equation becomes:
\[ x + 6(-1) = -3 \]
\[ x - 6 = -3 \implies x = +3 \]
- So, Cr in \( \text{Cr(CN)}_6^{3-} \) is +3.

- **For \( \text{NiF}_6^{2-} \)**:
- The oxidation state of F is -1.
- Let the oxidation state of Ni be \( x \).
- The equation becomes:
\[ x + 6(-1) = -2 \]
\[ x - 6 = -2 \implies x = +4 \]
- So, Ni in \( \text{NiF}_6^{2-} \) is +4.

- **For \( \text{CrO}_2\text{Cl}_2 \)**:
- The oxidation state of O is -2 and Cl is -1.
- Let the oxidation state of Cr be \( x \).
- The equation becomes:
\[ x + 2(-2) + 2(-1) = 0 \]
\[ x - 4 - 2 = 0 \implies x = +6 \]
- So, Cr in \( \text{CrO}_2\text{Cl}_2 \) is +6.

3. **Conclusion**:
- The species with an atom in the +6 oxidation state is \( \text{Cr}_2\text{O}_7^{2-} \) and \( \text{CrO}_2\text{Cl}_2 \).

### Final Answer:
The species with an atom in +6 oxidation state is \( \text{CrO}_2\text{Cl}_2 \).