The colour of `FeF_3` is

Options

A. Brown
B. Red Brown
C. Light green
D. White

Explanation

To determine the color of FeF₃ (iron(III) fluoride), we can follow these steps:

### Step 1: Identify the oxidation state of iron in FeF₃
FeF₃ consists of iron and fluoride ions. The fluoride ion (F⁻) has a charge of -1. Since there are three fluoride ions, the total negative charge is -3. To balance this, iron must have a charge of +3. Therefore, the oxidation state of iron in FeF₃ is +3.

### Step 2: Determine the electronic configuration of iron in the +3 oxidation state
The atomic number of iron (Fe) is 26. The electronic configuration of neutral iron is:
\[ \text{Fe: } [\text{Ar}] 3d^6 4s^2 \]
When iron is in the +3 oxidation state, it loses two 4s electrons and one 3d electron, resulting in:
\[ \text{Fe}^{3+}: [\text{Ar}] 3d^5 \]

### Step 3: Analyze the ligand field strength of fluoride ions
Fluoride ions (F⁻) are considered weak field ligands. Weak field ligands do not cause significant splitting of the d-orbitals in transition metal complexes. As a result, there is no pairing of electrons in the 3d subshell of Fe³⁺.

### Step 4: Consider the possibility of d-d transitions
In transition metal complexes, color is often observed due to d-d transitions, where electrons jump from a lower energy d-orbital to a higher energy d-orbital. However, since fluoride is a weak field ligand and does not cause pairing of electrons, there are no d-d transitions occurring in FeF₃.

### Step 5: Conclude the color of FeF₃
Since there are no d-d transitions and no unpaired electrons to contribute to color, FeF₃ does not exhibit any color. It is typically described as white.

### Final Answer:
The color of FeF₃ is white.

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