Which of the following specie is diamagnetic in nature ?

Options

A. `[Cr(NH_3_6]^(3+)`
B. `[Fe(NH_3)_6]^(2+)`
C. `[Co(H_2O)_6]^(+2)`
D. `[NiF_6]^(4-)`

Answer

To determine which of the following species is diamagnetic in nature, we need to analyze the electron configurations of each species and check for the presence of unpaired electrons. A diamagnetic species is one that has all its electrons paired, while a paramagnetic species has one or more unpaired electrons.

### Step-by-Step Solution:

1. **Identify the Species**: The species given are Cr (Chromium), Fe(NH3)6^2+, Co(H2O)6^2+, and NiF6^4-.

2. **Determine the Oxidation States**:
- For **Cr**: In its elemental form, Chromium has an oxidation state of 0. However, we need to consider its +3 state in this context.
- For **Fe(NH3)6^2+**: Ammonia (NH3) is a neutral ligand, so the oxidation state of iron (Fe) here is +2.
- For **Co(H2O)6^2+**: Water (H2O) is also a neutral ligand, so cobalt (Co) has an oxidation state of +2.
- For **NiF6^4-**: Fluorine (F) has a -1 charge, and with 6 fluorine atoms, the total negative charge is -6. Therefore, nickel (Ni) must have an oxidation state of +2 to balance the -6 charge to give a total of -4.

3. **Determine Electron Configurations**:
- **Cr^3+**: The electron configuration of Cr is [Ar] 4s^1 3d^5. For Cr^3+, we remove 3 electrons (1 from 4s and 2 from 3d), resulting in [Ar] 3d^3. This has 3 unpaired electrons.
- **Fe^2+**: The electron configuration of Fe is [Ar] 4s^2 3d^6. For Fe^2+, we remove 2 electrons (both from 4s), resulting in [Ar] 3d^6. This has 4 unpaired electrons.
- **Co^2+**: The electron configuration of Co is [Ar] 4s^2 3d^7. For Co^2+, we remove 2 electrons (both from 4s), resulting in [Ar] 3d^7. This has 3 unpaired electrons.
- **Ni^2+**: The electron configuration of Ni is [Ar] 4s^2 3d^8. For Ni^2+, we remove 2 electrons (both from 4s), resulting in [Ar] 3d^8. This has 2 unpaired electrons.

4. **Conclusion**: All the species mentioned (Cr^3+, Fe^2+, Co^2+, and Ni^2+) have unpaired electrons, indicating that they are all paramagnetic. Therefore, none of the species listed are diamagnetic.

### Final Answer:
None of the species listed (Cr^3+, Fe(NH3)6^2+, Co(H2O)6^2+, NiF6^4-) are diamagnetic.