Write the Lewis structure for the NH4 + ion.
The Correct Answer and Explanation is:
Lewis Structure for NH₄⁺ (Ammonium Ion):
Correct Lewis Structure:
H
|
H – N⁺ – H
|
H
Each hydrogen (H) forms a single bond with the central nitrogen (N) atom. Nitrogen has a formal positive charge in this structure.
Explanation:
The ammonium ion (NH₄⁺) is a polyatomic ion formed when ammonia (NH₃) accepts a proton (H⁺). To understand its structure, we use Lewis dot structures, which show how valence electrons are distributed in a molecule or ion.
Nitrogen (N) has 5 valence electrons, and each hydrogen (H) has 1. In total, we begin with:
- Nitrogen: 5 electrons
- Hydrogen (4 × 1): 4 electrons
- Total: 9 electrons
But NH₄⁺ has a +1 charge, meaning it has lost one electron. So we adjust the total number of electrons:
9 – 1 = 8 valence electrons to distribute.
To satisfy the octet rule, nitrogen forms four single bonds with four hydrogen atoms. Each N–H bond uses two electrons, and 4 bonds × 2 electrons = 8 electrons, which matches our available count.
After forming four single bonds, nitrogen has 8 electrons around it (2 per bond), achieving a complete octet. Each hydrogen has only 2 electrons (a single bond), which is sufficient because hydrogen follows the duet rule.
Since nitrogen normally forms three bonds (like in NH₃), forming four bonds gives it a formal positive charge, because it is effectively “sharing” one more electron than usual. The ion’s positive charge is indicated on nitrogen in the Lewis structure.
Also, because this is a charged ion, the entire Lewis structure should be placed inside brackets with the charge outside:
[ H
|
H – N⁺ – H ]⁺
|
H
In summary, NH₄⁺ has a central nitrogen atom bonded to four hydrogen atoms, uses 8 electrons total, satisfies all atoms’ valence needs, and carries a positive charge due to the extra proton accepted by NH₃.
