…………… hybrid orbitals of nitrogen atom are involved in the formation of ammonium ion.

Explanation

To determine the hybrid orbitals of the nitrogen atom involved in the formation of the ammonium ion (NH4+), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Ammonium Ion**:
The ammonium ion is represented as NH4+. This indicates that nitrogen is bonded to four hydrogen atoms and carries a positive charge.

2. **Determine the Electronic Configuration of Nitrogen**:
The atomic number of nitrogen is 7. Its electronic configuration is:
- 1s² 2s² 2p³

3. **Count the Valence Electrons**:
In the outer shell (2nd shell), nitrogen has:
- 2 electrons in the 2s orbital
- 3 electrons in the 2p orbitals
This gives a total of 5 valence electrons.

4. **Understand Hybridization**:
To form bonds with four hydrogen atoms, nitrogen needs to utilize its orbitals. Since nitrogen has no d-orbitals available (as it is in the second period of the periodic table), it can only hybridize its s and p orbitals.

5. **Determine the Type of Hybridization**:
For nitrogen to form four equivalent bonds (one with each hydrogen atom), it undergoes sp³ hybridization. This involves mixing one s orbital and three p orbitals to create four equivalent sp³ hybrid orbitals.

6. **Formation of Ammonium Ion**:
In the ammonium ion, the four sp³ hybrid orbitals of nitrogen will form sigma bonds with the four hydrogen atoms. The lone pair that nitrogen originally had is used to bond with an additional hydrogen atom, resulting in a positively charged ion.

7. **Conclusion**:
Therefore, the hybrid orbitals of nitrogen involved in the formation of the ammonium ion are sp³ hybridized orbitals.

### Final Answer:
**sp³ hybridized orbitals of nitrogen are involved in the formation of ammonium ion.**

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