In the transition element the incoming electron occupies `[n-1]` d sublevel in preference to

Options

A. np
B. ns
C. `[n-1]d`
D. `[n+1]d`

Explanation

To solve the question regarding the preference of electron filling in transition elements, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Electron Configuration**:
- In transition elements, the electron configuration follows a specific order based on the Aufbau principle. Electrons fill orbitals starting from the lowest energy level to the highest.

2. **Identifying the Shells**:
- For transition metals, the relevant shells are the n-s, (n-1)d, and n-p orbitals. Here, 'n' represents the principal quantum number of the outermost shell.

3. **Filling Order**:
- The filling order of electrons in transition metals typically goes as follows:
- First, the n-s orbital is filled.
- Next, the (n-1)d orbital is filled.
- Finally, the n-p orbital is filled.

4. **Preference for (n-1)d Sublevel**:
- The question asks why the incoming electron occupies the (n-1)d sublevel in preference to another sublevel. The reason is that the (n-1)d sublevel is of lower energy compared to the n-p sublevel when considering the transition elements.

5. **Conclusion**:
- Therefore, in transition elements, the incoming electron occupies the (n-1)d sublevel in preference to the n-p sublevel.

### Final Answer:
In transition elements, the incoming electron occupies the (n-1)d sublevel in preference to the n-p sublevel.

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