Question

For each of the following molecules, indicate the bond angle expected between the central atom and any two adjacent chlorine atoms. a. \(\mathrm{Cl}_{2} \mathrm{O}\) b. CCl \(_{4}\) c. \(\mathrm{BeCl}_{2}\)

Short answer

The bond angles between the central atom and any two adjacent chlorine atoms for the given molecules are as follows: a. Cl2O: bond angle ≈ \(104.5^\circ\) b. CCl4: bond angle ≈ \(109.5^\circ\) c. BeCl2: bond angle = \(180^\circ\)

Step-by-step solution

Determine the VSEPR geometry for each molecule

For each molecule, we will determine the geometry based on the number of electron pairs surrounding the central atom. Keep in mind that VSEPR theory involves the analysis of electron domains (bonding and non-bonding) surrounding a central atom. a. \(\mathrm{Cl}_{2} \mathrm{O}\) The central atom in Cl2O is oxygen (O). Oxygen has six valence electrons, three of which form covalent bonds with chlorine atoms. The remaining two electrons form a lone pair. Consequently, there are three electron domains: two bonding domains, and one non-bonding domain. According to VSEPR, this corresponds to a "bent" geometry. b. CCl \(_{4}\) The central atom in CCl4 is carbon (C). Carbon has four valence electrons, each of which forms a covalent bond with a chlorine atom, resulting in a total of four bonding domains. According to VSEPR, this corresponds to a "tetrahedral" geometry. c. \(\mathrm{BeCl}_{2}\) The central atom in BeCl2 is beryllium (Be). Beryllium has two valence electrons, both of which form covalent bonds with chlorine atoms, resulting in a total of two bonding domains. According to VSEPR, this corresponds to a "linear" geometry.

Determine bond angles for each molecule

Now that we've established the molecular geometry for each molecule, we can determine the bond angles between the central atom and any two adjacent chlorine atoms. a. \(\mathrm{Cl}_{2} \mathrm{O}\) The bond angle for a bent molecule is approximately \(104.5^\circ\). Therefore, the bond angle between Oxygen and any two adjacent chlorine atoms in Cl2O is approximately \(104.5^\circ\). b. CCl \(_{4}\) The bond angle for a tetrahedral molecule is approximately \(109.5^\circ\). Therefore, the bond angle between carbon and any two adjacent chlorine atoms in CCl4 is approximately \(109.5^\circ\). c. \(\mathrm{BeCl}_{2}\) The bond angle for a linear molecule is \(180^\circ\). Therefore, the bond angle between beryllium and any two adjacent chlorine atoms in BeCl2 is \(180^\circ\). To summarize: a. Cl2O: bond angle ≈ \(104.5^\circ\) b. CCl4: bond angle ≈ \(109.5^\circ\) c. BeCl2: bond angle = \(180^\circ\)

Key concepts

Molecular Geometry

When studying chemical compounds, understanding the arrangement of atoms within molecules, or molecular geometry, is crucial. Molecular geometry captures the three-dimensional structure of molecules, which is a direct consequence of the chemical bonding patterns in the molecule. Interestingly, the geometrical structure largely determines the properties and behavior of a substance.

VSEPR (Valence Shell Electron Pair Repulsion) theory is fundamental when predicting molecular geometry. It states that the shapes of molecules are influenced by the repulsion between electron pairs in the valence shell of the central atom. These electron pairs include both bonding pairs, which link atoms together, and lone pairs, which are unbonded. By minimizing repulsion among these electron pairs, distinct geometric arrangements emerge.

For example, in our exercise solutions, different molecules had a variety of shapes: bent, tetrahedral, and linear geometries. Cl₂O with its 'bent' geometry, CCl₄ with a 'tetrahedral' shape, and BeCl₂ with a 'linear' configuration. Each distinct geometry affects the chemical properties and reactivity of the molecule.

Chemical Bonding

Chemical bonding is at the heart of chemistry. Bonds are forces of attraction that hold atoms together in molecules and compounds. There are several types of chemical bonds, with covalent, ionic, and metallic bonds being the primary categories.

In a covalent bond, atoms share pairs of electrons, bringing them closer together and stabilizing the molecule. Covalent bonding is the key player in the molecular geometries discussed in the VSEPR theory. In our textbook examples, covalent bonds between the central atom and the chlorine atoms define the structure of each molecule. For instance, in Cl₂O, oxygen shares electrons with chlorine atoms, forging strong covalent bonds.

Understanding how these bonds form and the number of bonding pairs around a central atom allows us to predict the molecular structure and, as a result, anticipate the properties and behavior of the substance.

Bond Angles

Closely related to molecular geometry is the concept of bond angles, the angle between two adjacent bonds originating from the same atom. Determining these angles is integral for visualizing molecular geometry and crucial for understanding molecular shape-dependent phenomena, such as molecular polarity and intermolecular forces.

Using VSEPR theory helps in reconciling why certain bond angles are consistent, such as roughly 104.5° for bent molecules like Cl₂O, around 109.5° for tetrahedral molecules like CCl₄, and exactly 180° for linear molecules like BeCl₂. Predicting these angles is essential for applications in molecular modeling and the analysis of chemical reactions.

In summary, bond angles, impacted by electron pair repulsions and molecular geometry, define the structural aspects of a molecule that dictate its reactivity and physical properties.