After np orbitals are filled, the next orbital filled will be :-

Options

A. `(n+1)s`
B. `(n+2)p`
C. `(n+1)d`
D. `(n+2)s`

Explanation

To determine which orbital is filled after the np orbitals, we can follow the steps outlined below:

### 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 is based on the increasing order of energy levels.

2. **Identify the Order of Orbital Filling**: The order of filling of orbitals is determined by the n + l rule, where n is the principal quantum number and l is the azimuthal quantum number. The lower the value of n + l, the lower the energy of the orbital.

3. **Determine the n + l Values**:
- For the **s orbital** (l = 0), the value is n + 0 = n.
- For the **p orbital** (l = 1), the value is n + 1.
- For the **d orbital** (l = 2), the value is n + 2.
- For the **f orbital** (l = 3), the value is n + 3.

4. **Fill the np Orbitals**: Once the np orbitals are filled, we need to look at the next orbital to be filled. The np orbitals have a principal quantum number of n, so they are filled before the n + 1 s orbital.

5. **Identify the Next Orbital**: After filling the np orbitals, the next set of orbitals to be filled will be the (n + 1)s orbital. This is because it has the lowest n + l value compared to the (n + 1)p or (n + 1)d orbitals.

6. **Conclusion**: Therefore, after the np orbitals are filled, the next orbital that will be filled is the (n + 1)s orbital.

### Final Answer:
The next orbital filled after np orbitals are filled will be the (n + 1)s orbital.

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