Which of the following statements is incorrect?
(i) In octahedral complexes, `t_(2g)` orbitals posses low energy as compared to `e_(g)` orbitals
(ii) In octahedral complexes, `e_(g)` orbitals possess low energy as compared to `t_(2g)` orbitals
(iii) In tetrahedral complexes, `t_(2g)` orbitals posses high energy as compared to `e_(g)` orbitals

Options

A. (ii) only
B. (iii) only
C. (i) and (ii)
D. (i) and (iii)

Answer

To determine which of the given statements is incorrect regarding octahedral and tetrahedral complexes, we need to analyze the energy levels of the d-orbitals in these complexes.

### Step-by-Step Solution:

1. **Understanding Octahedral Complexes:**
- In octahedral complexes, the five d-orbitals split into two groups due to the presence of ligands.
- The lower energy set of orbitals is called `t_(2g)` (which includes dxy, dyz, dzx), and the higher energy set is called `e_(g)` (which includes dx²-y² and dz²).
- Therefore, the statement "In octahedral complexes, `t_(2g)` orbitals possess low energy as compared to `e_(g)` orbitals" is **correct**.

2. **Analyzing the Second Statement:**
- The second statement claims that "In octahedral complexes, `e_(g)` orbitals possess low energy as compared to `t_(2g)` orbitals."
- This is **incorrect** because `e_(g)` orbitals are at a higher energy level than `t_(2g)` orbitals in octahedral complexes.

3. **Understanding Tetrahedral Complexes:**
- In tetrahedral complexes, the d-orbitals also split, but the energy arrangement is different.
- The orbitals split into two groups: the lower energy set is `e` (which includes dxy, dyz, dzx) and the higher energy set is `t_(2g)` (which includes dx²-y² and dz²).
- The statement "In tetrahedral complexes, `t_(2g)` orbitals possess high energy as compared to `e_(g)` orbitals" is **correct**.

4. **Conclusion:**
- The incorrect statement among the options is the second one: "In octahedral complexes, `e_(g)` orbitals possess low energy as compared to `t_(2g)` orbitals".

### Final Answer:
The incorrect statement is: **(ii) In octahedral complexes, `e_(g)` orbitals possess low energy as compared to `t_(2g)` orbitals.**

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