Draw the Lewis structure and predict the molecu- lar geometry of the following molecules

Draw the Lewis structure and predict the molecu- lar geometry of the following molecules: a. SO2 b. CI4 c. BCl3

The Correct Answer and Explanation is:

Let’s go over the Lewis structures and molecular geometries for the molecules: SO₂, CCl₄, and BCl₃.

a) SO₂ (Sulfur Dioxide)

Step 1: Lewis Structure

• Sulfur (S) is the central atom, with oxygen (O) atoms bonded to it.
• Sulfur has 6 valence electrons, and each oxygen has 6 valence electrons. SO₂ has 16 valence electrons in total (6 + 2 × 6 = 18).
• Draw a single bond between sulfur and each oxygen, and distribute the remaining electrons to satisfy the octet rule.
• A double bond is formed between sulfur and each oxygen to complete the octet for both oxygen atoms and satisfy sulfur’s requirement for 12 valence electrons (octet expanded in sulfur).

The Lewis structure will be:

O = S = O

Step 2: Molecular Geometry

• In SO₂, the sulfur atom has two bonding pairs of electrons and one lone pair. The electron pairs around the sulfur will arrange themselves to minimize repulsion.
• This results in a bent molecular geometry with a bond angle of approximately 120°, characteristic of a molecule with sp² hybridization.

b) CCl₄ (Carbon Tetrachloride)

Step 1: Lewis Structure

• Carbon (C) is the central atom, with chlorine (Cl) atoms bonded to it.
• Carbon has 4 valence electrons, and each chlorine atom has 7 valence electrons. CCl₄ has 32 valence electrons in total (4 + 4 × 7 = 32).
• Form single bonds between carbon and each chlorine atom and place the remaining electrons as lone pairs on the chlorine atoms.

The Lewis structure will be:

     Cl
     |
Cl - C - Cl
     |
     Cl

Step 2: Molecular Geometry

• In CCl₄, carbon has four bonding pairs of electrons and no lone pairs. These bonding pairs will arrange themselves in a way that minimizes repulsion, forming a tetrahedral geometry with bond angles of 109.5°.
• The carbon atom is sp³ hybridized.

c) BCl₃ (Boron Trichloride)

Step 1: Lewis Structure

• Boron (B) is the central atom, with chlorine (Cl) atoms bonded to it.
• Boron has 3 valence electrons, and each chlorine atom has 7 valence electrons. BCl₃ has 24 valence electrons in total (3 + 3 × 7 = 24).
• Form single bonds between boron and each chlorine atom, and place the remaining electrons as lone pairs on chlorine.

The Lewis structure will be:

     Cl
     |
Cl - B - Cl

Step 2: Molecular Geometry

• In BCl₃, boron has three bonding pairs of electrons and no lone pairs. These bonding pairs will arrange themselves to minimize repulsion, resulting in a trigonal planar molecular geometry with bond angles of 120°.
• The boron atom is sp² hybridized.

Summary of Molecular Geometries:

• SO₂: Bent (120°), sp² hybridization.
• CCl₄: Tetrahedral (109.5°), sp³ hybridization.
• BCl₃: Trigonal planar (120°), sp² hybridization.

Each molecule follows the general rules of the Valence Shell Electron Pair Repulsion (VSEPR) theory, predicting the geometry based on the electron pairs around the central atom.