Question

In the hybrid orbital model, compare and contrast \(\sigma\) bonds with \(\pi\) bonds. What orbitals form the \(\sigma\) bonds and what orbitals form the \(\pi\) bonds? Assume the \(z\) -axis is the internuclear axis.

Short answer

In the hybrid orbital model, \(\sigma\) bonds are formed by end-to-end overlap of atomic orbitals, such as s-s, s-p, and p-p (specifically p\(_z\)) combinations, while \(\pi\) bonds are formed by side-by-side overlap of p\(_x\) or p\(_y\) orbitals. The \(\sigma\) bond has electron density concentrated along the internuclear axis, while the \(\pi\) bond has two regions of electron density above and below the internuclear axis.

Step-by-step solution

Definition of Sigma and Pi bonds.

A \(\sigma\) bond is a covalent bond formed between two atoms by the end-to-end (head-on) overlapping of their atomic orbitals. This overlapping forms a region of high electron density along the internuclear axis, which is the z-axis in this case. A \(\pi\) bond, on the other hand, is another type of covalent bond formed between two atoms when their atomic orbitals overlap side-by-side. This overlapping creates two regions of high electron density above and below the internuclear axis.

Orbitals that form Sigma bonds

In the hybrid orbital model, the atomic orbitals involved in the formation of \(\sigma\) bonds are: 1. s orbitals: An s orbital can overlap with another s orbital head-on, forming an \(\text{s-s}\) \(\sigma\) bond. 2. s and p orbitals: An s orbital can also overlap with a p orbital along the internuclear axis, resulting in an \(\text{s-p}\) \(\sigma\) bond. 3. p orbitals: A p orbital, specifically the one aligned along the z-axis (p\(_z\)), can overlap with another p\(_z\) orbital head-on, creating a \(\text{p-p}\) \(\sigma\) bond.

Orbitals that form Pi bonds

In the hybrid orbital model, the atomic orbitals involved in the formation of \(\pi\) bonds are: 1. p orbitals: The p orbitals responsible for forming \(\pi\) bonds are the ones not aligned along the internuclear axis (z-axis). These are the p\(_x\) and p\(_y\) orbitals. They can interact with each other in a side-by-side fashion to form a \(\pi\) bond. In summary, the hybrid orbital model shows that \(\sigma\) and \(\pi\) bonds are formed by different types of atomic orbital overlap. \(\sigma\) bonds are created through end-to-end overlap of orbitals (like s, s-p, p-p), while \(\pi\) bonds are established by side-by-side overlap of p orbitals (p\(_x\) or p\(_y\)).