Which of the following statement is not true?

Q: Which of the following statement is not true?

Option 3 is the correct answer because it states that $[FeF_{6}]^{3-}$ is an inner orbital complex, which is not true. Let's delve into the reasoning: 1. **Explanation for Option 3:** - $[FeF_{6}]^{3-}$ involves the fluoride ion, which is a weak field ligand according to the spectrochemical series. Weak field ligands do not cause significant splitting of the d-orbitals, leading to high spin complexes. In high spin complexes, the electrons occupy the outer d-orbitals, resulting in an outer orbital complex. Therefore, $[FeF_{6}]^{3-}$ is actually an outer orbital complex, not an inner orbital complex. This makes Option 3 the correct choice as it is the statement that is not true. 2. **Explanation for why other options are incorrect:** - **Option 1:** Halide ligands, such as chloride, bromide, and fluoride, are generally weak field ligands. They cause small splitting of the d-orbitals, leading to high spin complexes. Therefore, the statement that halide ligands form high spin complexes is true. - **Option 2:** Strong ligands, such as CN$^-$ and CO, cause large splitting of the d-orbitals, which often results in low spin complexes. This is because the energy required to pair electrons in the lower energy d-orbitals is less than the energy required to place them in the higher energy orbitals. Thus, the statement that strong ligands form low spin complexes is true. - **Option 4:** $[NiCl_{4}]^{2-}$ involves the chloride ion, which is a weak field ligand. This leads to a high spin configuration where the electrons occupy the outer d-orbitals, making it an outer orbital complex. Therefore, the statement that $[NiCl_{4}]^{2-}$ is an outer orbital complex is true. In conclusion, Option 3 is the correct answer because it incorrectly describes $[FeF_{6}]^{3-}$ as an inner orbital complex, whereas it is actually an outer orbital complex. The other options correctly describe the nature of the complexes they refer to.

Question

Accepted Answer

Option 3 is the correct answer because it states that $[FeF_{6}]^{3-}$ is an inner orbital complex, which is not true. Let's delve into the reasoning:

1. **Explanation for Option 3:**
   - $[FeF_{6}]^{3-}$ involves the fluoride ion, which is a weak field ligand according to the spectrochemical series. Weak field ligands do not cause significant splitting of the d-orbitals, leading to high spin complexes. In high spin complexes, the electrons occupy the outer d-orbitals, resulting in an outer orbital complex. Therefore, $[FeF_{6}]^{3-}$ is actually an outer orbital complex, not an inner orbital complex. This makes Option 3 the correct choice as it is the statement that is not true.

2. **Explanation for why other options are incorrect:**

- **Option 1:** Halide ligands, such as chloride, bromide, and fluoride, are generally weak field ligands. They cause small splitting of the d-orbitals, leading to high spin complexes. Therefore, the statement that halide ligands form high spin complexes is true.

- **Option 2:** Strong ligands, such as CN$^-$ and CO, cause large splitting of the d-orbitals, which often results in low spin complexes. This is because the energy required to pair electrons in the lower energy d-orbitals is less than the energy required to place them in the higher energy orbitals. Thus, the statement that strong ligands form low spin complexes is true.

- **Option 4:** $[NiCl_{4}]^{2-}$ involves the chloride ion, which is a weak field ligand. This leads to a high spin configuration where the electrons occupy the outer d-orbitals, making it an outer orbital complex. Therefore, the statement that $[NiCl_{4}]^{2-}$ is an outer orbital complex is true.

In conclusion, Option 3 is the correct answer because it incorrectly describes $[FeF_{6}]^{3-}$ as an inner orbital complex, whereas it is actually an outer orbital complex. The other options correctly describe the nature of the complexes they refer to.