In which of the following compounds transition metal has zero oxidation state ?

Options

A. `Fe(CO)_(5)`
B. `NH_(2).NH_(2)`
C. `NOClO_(4)`
D. `CrO_(5)`

Explanation

To determine which compound contains a transition metal in the zero oxidation state, we will analyze each of the given compounds step by step.

### Step 1: Identify the Compounds
The compounds given are:
1. NH2NH2 (Hydrazine)
2. NOClO4 (Perchlorate)
3. Fe(CO)5 (Iron pentacarbonyl)
4. CrO5 (Chromium pentoxide)

### Step 2: Eliminate Non-Transition Metal Compounds
First, we need to check if there are any transition metals in the first two compounds:
- **NH2NH2**: This compound contains nitrogen and hydrogen only, no transition metals.
- **NOClO4**: This compound contains nitrogen, oxygen, and chlorine, but no transition metals.

Since both NH2NH2 and NOClO4 do not contain transition metals, we can eliminate these options.

### Step 3: Analyze Fe(CO)5
Next, we analyze **Fe(CO)5**:
- Carbon monoxide (CO) is a neutral ligand, meaning it does not contribute to the oxidation state of the metal.
- Let the oxidation state of iron (Fe) be \( X \).
- The equation for the oxidation state can be set up as follows:
\[ X + (0 \times 5) = 0 \]
Here, the total charge of the compound is zero.
- Therefore, \( X = 0 \).

### Step 4: Analyze CrO5
Now we analyze **CrO5**:
- The structure of CrO5 consists of one chromium atom and five oxygen atoms, where four of the oxygen atoms are in the form of peroxides (O2^2-).
- Let the oxidation state of chromium (Cr) be \( Y \).
- The equation for the oxidation state can be set up as follows:
\[ Y + (-2) + 4 \times (-1) = 0 \]
Here, -2 is for the oxide ion and -1 for each of the four peroxide ions.
- Simplifying this gives:
\[ Y - 2 - 4 = 0 \implies Y - 6 = 0 \implies Y = +6 \]

### Step 5: Conclusion
From our analysis:
- In **Fe(CO)5**, the oxidation state of Fe is 0.
- In **CrO5**, the oxidation state of Cr is +6.

Thus, the compound in which the transition metal has a zero oxidation state is **Fe(CO)5**.

### Final Answer
The transition metal with zero oxidation state is found in **Fe(CO)5**.

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