Q.Which of the following species have the same shape? (Note: more than one of the given options may be correct.)

The shapes of molecules are determined by the Valence Shell Electron Pair Repulsion (VSEPR) theory, which predicts geometry based on minimizing repulsion between electron pairs around the central atom.

Here's the analysis for each species:

1. CO$_2$: The central carbon atom forms two double bonds with two oxygen atoms and has no lone pairs. This results in 2 electron domains, leading to a linear shape.
2. CCl$_4$: The central carbon atom forms four single bonds with four chlorine atoms and has no lone pairs. This results in 4 electron domains, leading to a tetrahedral shape.
3. O$_3$: The central oxygen atom forms one single bond and one double bond with the two terminal oxygen atoms, and it has one lone pair. This results in 3 electron domains (2 bonding pairs + 1 lone pair), leading to a bent shape. …

Understanding molecular shapes is fundamental in chemistry, as it dictates a molecule's properties, reactivity, and interactions. The Valence Shell Electron Pair Repulsion (VSEPR) theory is our primary tool for predicting these shapes.

The core idea behind VSEPR theory is that electron pairs (both bonding pairs and lone pairs) around a central atom will arrange themselves in three-dimensional space to minimize repulsion between them. This arrangement determines the electron domain geometry. Once we know the electron domain geometry, we then consider only the positions of the atoms (ignoring lone pairs) to determine the molecular geometry, which is the actual "shape" of the molecule.

Here's how we apply VSEPR theory to each species:

1. Carbon Dioxide ($\text{CO}_2$)

1. Identify the central atom: Carbon (C) is the central atom, as it is less electronegative than oxygen and forms bonds with two oxygen atoms.
2. Count total valence electrons:
   • Carbon: 4 valence electrons
   • Oxygen: 6 valence electrons $\times$ 2 atoms = 12 valence electrons
   • Total = $4 + 12 = 16$ valence electrons.
3. Draw the Lewis structure: The most stable Lewis structure for $\text{CO}_2$ has carbon double-bonded to each oxygen atom.

Each oxygen has two lone pairs, completing its octet. Carbon also has an octet.

4. Determine electron domains around the central atom: The central carbon atom has two double bonds. Each double bond counts as one electron domain.

* Number of bonding domains = 2

* Number of lone pairs = 0

* Total electron domains (steric number) = $2 + 0 = 2$.

5. Predict electron domain geometry: With 2 electron domains, the electron domains arrange themselves linearly to minimize repulsion.

6. Predict molecular geometry (shape): Since there are no lone pairs on the central atom, the molecular geometry is the same as the electron domain geometry.

* Shape: Linear

* Bond angle: $180^\circ$

2. Carbon Tetrachloride ($\text{CCl}_4$)

1. Identify the central atom: Carbon (C) is the central atom.
2. Count total valence electrons:
   • Carbon: 4 valence electrons
   • Chlorine: 7 valence electrons $\times$ 4 atoms = 28 valence electrons
   • Total = $4 + 28 = 32$ valence electrons.
3. Draw the Lewis structure: Carbon forms single bonds with four chlorine atoms. Each chlorine atom has three lone pairs to complete its octet. Carbon also has an octet.

4. Determine electron domains around the central atom: The central carbon atom has four single bonds.
   • Number of bonding domains = 4
   • Number of lone pairs = 0
   • Total electron domains (steric number) = $4 + 0 = 4$.
5. Predict electron domain geometry: With 4 electron domains, the electron domains arrange themselves tetrahedrally.
6. Predict molecular geometry (shape): Since there are no lone pairs on the central atom, the molecular geometry is the same as the electron domain geometry.
   • Shape: Tetrahedral
   • Bond angle: $109.5^\circ$

3. Ozone ($\text{O}_3$)

1. Identify the central atom: The middle oxygen atom is the central atom.
2. Count total valence electrons:
   • Oxygen: 6 valence electrons $\times$ 3 atoms = 18 valence electrons.
3. Draw the Lewis structure: Ozone exhibits resonance. One resonance structure shows the central oxygen double-bonded to one oxygen and single-bonded to the other, with a lone pair on the central oxygen.

For VSEPR, we consider the electron domains around the central atom in one of these resonance forms.

4. Determine electron domains around the central atom: The central oxygen atom has one double bond, one single bond, and one lone pair.

* Number of bonding domains = 2 (one double bond + one single bond)

* Number of lone pairs = 1

* Total electron domains (steric number) = $2 + 1 = 3$.

5. Predict electron domain geometry: With 3 electron domains, the electron domains arrange themselves in a trigonal planar geometry. …