Question

Identify the molecule (X) with maximum number of lone pairs of electrons (obtained using Lewis dot structure) among HNO₃, H₂SO₄, NF₃, and O₃. Choose the correct bond angle made by the central atom of the molecule (X).

• A. 116°
• B. 120°
• C. 107°
• D. 102°

Hint:

In NF₃, the bond angle (102°) is smaller than in NH₃ (107°) because the highly electronegative F atoms pull the bonding electrons away from the central atom, reducing bond-pair bond-pair repulsion.

Answer 1

The Correct Option is D

To identify the molecule (X) with the maximum number of lone pairs of electrons, we will examine the Lewis structures of the given molecules: HNO₃, H₂SO₄, NF₃, and O₃.

1. HNO₃ (Nitric Acid): In the Lewis structure of HNO₃, nitrogen is the central atom. It forms one N=O double bond, one N-O single bond, and an N-OH bond. There are no lone pairs on the nitrogen atom as it completes its octet with bonds.
2. H₂SO₄ (Sulfuric Acid): In H₂SO₄, sulfur is the central atom. It forms two S=O double bonds and two S-O single bonds (bonded with hydrogen atoms). Similar to HNO₃, there are no lone pairs on the sulfur atom.
3. NF₃ (Nitrogen Trifluoride): In NF₃, nitrogen is the central atom. It forms three covalent bonds with fluorine atoms and has one lone pair of electrons. In this molecule, the lone pairs of electrons are present only on the nitrogen atom.
4. O₃ (Ozone): In the Lewis structure of ozone, one oxygen atom is centrally bonded, forming one O=O double bond and one O-O single bond. The central oxygen atom has one lone pair of electrons, and each outer oxygen atom has two lone pairs.

Considering the number of lone pairs overall in the molecule, NF₃ has the most lone pairs concentrated on the central atom.

Now for the bond angle question, NF₃ is a trigonal pyramidal molecule with a bond angle typically around \(102^\circ\). This is due to the repulsion caused by the lone pair-bond pair interactions which reduce the ideal tetrahedral angle (109.5°) to about 102°.

Thus, the molecule with the maximum lone pairs of electrons is NF₃, and the correct bond angle made by the central atom is \(102^\circ\).