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

Options

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

Answer

To solve the question, we need to analyze each of the statements regarding the energy levels of the d-orbitals in octahedral and tetrahedral complexes according to crystal field theory.

### Step-by-Step Solution:

1. **Statement (i)**: In octahedral complexes, `t_(2g)` orbitals possess low energy as compared to `e_(g)` orbitals.
- **Analysis**: In octahedral complexes, the d-orbitals split into two sets: the lower energy `t_(2g)` orbitals and the higher energy `e_(g)` orbitals. Therefore, this statement is **correct**.

2. **Statement (ii)**: In tetrahedral complexes, `t_(2)` orbitals possess high energy as compared to `e` orbitals.
- **Analysis**: In tetrahedral complexes, the splitting of d-orbitals is opposite to that in octahedral complexes. The `e` orbitals are lower in energy, while the `t_(2)` orbitals are higher in energy. Hence, this statement is also **correct**.

3. **Statement (iii)**: In octahedral complexes, `e_(g)` orbitals possess low energy as compared to `t_(2g)` orbitals.
- **Analysis**: This statement contradicts the established understanding of d-orbital splitting in octahedral complexes. The `e_(g)` orbitals are higher in energy than the `t_(2g)` orbitals. Therefore, this statement is **incorrect**.

### Conclusion:
- The correct statements are (i) and (ii). Thus, the answer is that statements (i) and (ii) are correct.

### Final Answer:
The correct options are (i) and (ii).

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