Drawing the Lewis Structure for NH4

To draw the Lewis structure for the ammonium ion (NH4 ), follow these steps:

Count the Total Valence Electrons

In NH4 , nitrogen (N) has 5 valence electrons and each hydrogen (H) has 1 valence electron. Since there are 4 hydrogen atoms, the total valence electrons are calculated as follows:

Valence electrons of N 5 Valence electrons of H (4 atoms) 4 × 1 4 Total valence electrons 5 4 9

Draw the Skeleton Structure

Place nitrogen in the center because hydrogen atoms cannot be central atoms. Surround it with 4 hydrogen atoms to form the skeleton structure:

Skeleton structure of NH4

Check the Octet Rule

With the skeleton structure, check the octet rule to ensure that each atom has a full valence shell of 8 electrons. Each hydrogen has 2 electrons (fulfilling its duet rule), and nitrogen has a total of 8 electrons around it (4 single bonds).

Calculate Formal Charge on N

The formal charge on nitrogen is calculated using the formula:

FC Valence electrons of N - [Non-bonding electrons 1/2 bonding electrons]

Here, non-bonding electrons 0 (since all electrons are in bonding pairs) and bonding electrons 8 (4 bonds × 2 electrons per bond).

FC 5 - [0 1/2 × 8] 5 - 4 1

This calculation confirms that nitrogen should carry a positive charge, confirming the NH4 structure.

Lewis structure of NH4

Electronic Geometry and Sp3 Hybridization

Ammonium (NH4 ) and ammonia (NH3) have the same electronic geometry due to sp3 hybridization. In ammonium, the nitrogen atom is quaternized with a formal positive charge, and this results in an sp3 hybridization with a bond angle of approximately 109.5°.

Each H-N-H bond angle in the ammonium ion is 109.5°, which is the typical tetrahedral angle associated with sp3 hybridization.

Conclusion

The Lewis structure of NH4 accurately represents the bonding and charge distribution in the ammonium ion. Understanding the steps to draw the Lewis structure and the corresponding electronic geometry is crucial for predicting and explaining the behavior of this positively charged ion.