Question

In \( \text{NO}_3^- \) ion, the number of bond pairs and lone pairs of electrons on the nitrogen atom are:

• A. \( 2, 2 \)
• B. \( 3, 1 \)
• C. \( 1, 3 \)
• D. \( 4, 0 \)

Hint:

To determine the bonding in ions, count the pairs of electrons shared as bond pairs and the non-shared pairs as lone pairs.

Answer 1

The Correct Option is D

To ascertain the quantity of bond pairs and lone pairs on the nitrogen atom within the NO₃^- ion, the Lewis structure must be constructed.

1. Calculate the total valence electron count:

• Nitrogen (N) contributes 5 valence electrons.
• Each of the three Oxygen (O) atoms contributes 6 valence electrons, totaling 3 * 6 = 18 valence electrons.
• The addition of a single negative charge introduces one more electron.
• Total valence electrons: 5 + 18 + 1 = 24 electrons.

2. Construct the skeletal structure:

Nitrogen serves as the central atom, with the three oxygen atoms bonded to it.

3. Distribute the electrons:

The Lewis structure for NO₃^- indicates that nitrogen forms three bonds with the oxygen atoms. One of these bonds is a double bond, while the remaining two are single bonds. The structure can be depicted as:

O

||

O - N - O^-

4. Identify bond pairs and lone pairs:

• Nitrogen forms three bonds (one double bond and two single bonds). Consequently, there are 3 bond pairs.
• Nitrogen possesses no lone pairs of electrons.

Thus, the count of bond pairs is 3, and the count of lone pairs is 0.

Final Answer: 3, 0

However, the provided options do not include 3,0. If the double bond is considered as two bond pairs, the closest option is 4,0. The accurate count is 3,0. If, however, the double bond is counted as two bond pairs, the result is 4,0. Therefore, option 4 is the most fitting among the given choices.

The correct selection from the provided options is option 4: 4, 0.