Question

Based on predicted bond angles from VSEPR theory, why is the ozone molecule, \(\mathrm{O}_{3}\), not a cyclic molecule?

Short answer

The ozone molecule, O3, is not a cyclic molecule because according to the Valence Shell Electron Pair Repulsion (VSEPR) theory, the molecule adopts a bent or V-shaped structure to minimize repulsion between the pairs of electrons around the central oxygen atom - two bonding pairs and one lone pair. A cyclic structure would require three atoms connected at angles of 120 degrees, which is not possible for ozone due to the presence of a lone pair of electrons.

Step-by-step solution

Understand the structure of Ozone Molecule

In an ozone molecule, three oxygen atoms are connected in a bent line, with a central oxygen atom bonded to two other oxygen atoms and carrying one lone pair of electrons.

Application of VSEPR Theory

According to the Valence Shell Electron Repulsion (VSEPR) theory, the pairs of electrons around the central atom will repel each other and arrange themselves as far apart as possible in three-dimensional space to minimize repulsion. In case of ozone molecule, as there are three regions of high electron density around the central oxygen atom - two bonding pairs and one lone pair, they will arrange themselves in such a way that minimizes repulsion. This arrangement leads to a V-shaped or bent structure, with an angle slightly less than 120 degrees between the oxygen-oxygen bonds.

Conclusion

According to the VSEPR theory's predictions, the ozone molecule's actual structure doesn't match with a cyclic structure where the molecules form a closed ring. To form a cycle or ring, three atoms must be connected at angles of 120 degrees, which is not possible for ozone due to the presence of a lone pair of electrons. Thus, ozone molecule cannot be a cyclic molecule.

Key concepts

Bond Angles Prediction

Understanding the prediction of bond angles in molecules is crucial for visualizing their three-dimensional structure. The Valence Shell Electron Pair Repulsion (VSEPR) theory is a simple and intuitive model that guides us in predicting these angles. According to VSEPR, electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion between them. This applies to both bonding pairs and lone pairs of electrons.

Lone pairs are slightly more repulsive than bonding pairs, causing bond angles to adjust accordingly. For example, in a water molecule (H_2O), the bond angle is less than the ideal tetrahedral angle of 109.5 degrees due to the repulsion of the two lone pairs on the oxygen atom. In ozone (O_3), we apply similar reasoning. With one lone pair and two bonding pairs on the central oxygen atom, the bond angles are predicted to be less than the ideal angle of 120 degrees in a trigonal planar arrangement. Hence, the repulsion leads to a bent molecular geometry rather than a cyclic one.

Ozone Molecular Structure

Ozone (O_3) is a fascinating molecule with a bent molecular structure. It consists of three oxygen atoms with a central oxygen that is bonded to the two others. This central atom also harbors a lone pair of electrons.

The structure of ozone is not linear but instead takes on a 'V' shape or bent geometry. The lone pair on the central oxygen atom occupies more space than bonding pairs, affecting the bond angles between the oxygen atoms. The molecular geometry of ozone is determined by the positions of atoms in three-dimensional space that results in the lowest possible repulsion between the electron pairs. Understanding the molecular structure of ozone is essential for grasping its physical properties and chemical behavior, which plays a significant role in atmospheric chemistry and environmental science.

Electron Pair Repulsion

The concept of electron pair repulsion is a cornerstone of the VSEPR theory. Electrons carry a negative charge and, as like charges repel, electron pairs around a central atom will push away from each other. This repulsion is responsible for the shape that a molecule takes.

There are several types of electron pairs to consider: bonding pairs that are shared between two atoms, and lone pairs that are found solely on one atom. Lone pairs require more space because their electron density is exclusively around one atom; thus, they have a greater repulsive force than bonding pairs.

Theoretical Applications

In application, the geometry of a molecule like ozone is influenced by the repulsion of the lone pair on the central oxygen. The lone pair pushes the bonding pairs away, resulting in a bent structure. Understanding how electron pair repulsion influences molecular geometry is fundamental to predicting the shape and properties of molecules.