Which of the following species will be diamagnetic

Options

A. `[Fe(CN)_(6)]^(4-)`
B. `[FeF_(6)]^(3-)`
C. `[Co(C_(2)O_(4))_(3)]^(4-)`
D. `[CoF_(6)]^(3-)`

Answer

To determine which of the given species is diamagnetic, we need to analyze the electron configurations and the presence of unpaired electrons in each species. A species is considered diamagnetic if all of its electrons are paired.

### Step-by-Step Solution:

1. **Understand the Definition of Diamagnetic:**
- A species is diamagnetic if it has no unpaired electrons. This means all electrons in the species are paired.

2. **Identify the Ligands:**
- Recognize that weak field ligands do not promote electron pairing, while strong field ligands do. This is crucial for determining the magnetic properties of the species.

3. **Analyze Each Option:**
- **Option A: [Fe(CN)₆]⁴⁻**
- Iron (Fe) has an atomic number of 26. In the +2 oxidation state, its electron configuration is [Ar] 3d⁶.
- CN⁻ is a strong field ligand, which causes pairing of electrons. The electron configuration after pairing is:
- 1, 2, 3, 4, 5, 6 (all paired).
- Therefore, this species is **diamagnetic**.

- **Option B: [FeF₆]²⁻**
- Iron (Fe) in this case is also in the +2 oxidation state, so it has the same configuration of [Ar] 3d⁶.
- F⁻ is a weak field ligand, which does not promote pairing. Thus, the configuration remains:
- 1, 2, 3, 4, 5, 6 (with unpaired electrons).
- Therefore, this species is **paramagnetic**.

- **Option C: [Co(C₂O₄)₂]²⁻**
- Cobalt (Co) has an atomic number of 27. In the +2 oxidation state, its electron configuration is [Ar] 3d⁷.
- C₂O₄²⁻ is a strong field ligand, which promotes pairing. The electron configuration after pairing is:
- 1, 2, 3, 4, 5, 6, 7 (with one unpaired electron).
- Therefore, this species is **paramagnetic**.

- **Option D: [Ni(CO)₄]**
- Nickel (Ni) has an atomic number of 28. In the 0 oxidation state, its electron configuration is [Ar] 3d⁸ 4s².
- CO is a strong field ligand, which promotes pairing. The electron configuration after pairing is:
- 1, 2, 3, 4, 5, 6, 7, 8 (all paired).
- Therefore, this species is **diamagnetic**.

4. **Conclusion:**
- The diamagnetic species from the options are **[Fe(CN)₆]⁴⁻** and **[Ni(CO)₄]**.
- However, since the question asks for which of the following species will be diamagnetic, the only option that fits the criteria is **[Fe(CN)₆]⁴⁻**.

### Final Answer:
The species that is diamagnetic is **[Fe(CN)₆]⁴⁻**.