When `3d` orbital is complete, the new electron will enter the

Options

A. 4s-orbitals
B. 4p-orbitals
C. 4d-orbitals
D. None of these

Explanation

To determine where the new electron will enter after the 3d orbital is complete, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Aufbau Principle**: The Aufbau principle states that electrons occupy the lowest energy orbitals first before moving to higher energy orbitals. This means we need to look at the energy levels of the orbitals to determine where the next electron will go.

2. **Identify the Order of Orbital Filling**: The order in which orbitals are filled is based on their energy levels. The general order of filling is:
- 1s
- 2s
- 2p
- 3s
- 3p
- 4s
- 3d
- 4p
- 5s
- 4d
- 5p
- 6s
- 4f
- 5d
- 6p
- 7s
- 5f
- 6d
- 7p

3. **Locate the 3d Orbital**: According to the filling order, after the 4s orbital is filled, the next electrons will fill the 3d orbital. Once the 3d orbital is complete, we need to find the next available orbital.

4. **Determine the Next Orbital After 3d**: After the 3d orbital is filled, the next orbital to be filled is the 4p orbital. The energy of the 4p orbital is lower than that of the 5s orbital, making it the next logical choice for an incoming electron.

5. **Conclusion**: Therefore, when the 3d orbital is complete, the new electron will enter the **4p orbital**.

### Final Answer:
The new electron will enter the **4p orbital**.

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