What is the Difference Between Hybridization and Overlapping

Hybridization and overlapping are two different concepts related to the bonding between atoms in molecules. Understanding the difference between hybridization and overlapping is fundamental in chemistry, especially in the study of molecular structure and bonding. 

What is the difference between hybridization and overlapping? Hybridization is a model that describes the process of mixing atomic orbitals to form new hybrid orbitals, whereas overlapping is the interaction of atomic orbitals from different atoms to form a covalent bond.

Key Areas Covered

1. What is Hybridization 
      – Definition, Features 
2. What is Overlapping
      – Definition, Features 
3. Similarities Between Hybridization and Overlapping
      – Outline of Common Features
4. Difference Between Hybridization and Overlapping
      – Comparison of Key Differences
5. FAQ: Hybridization and Overlapping
      – Frequently Asked Questions

Key Terms

Hybridization, Overlapping, Orbital

What is Hybridization

Hybridization is a concept in chemistry that describes the process by which atomic orbitals within an atom mix to form new hybrid orbitals. Hybrid orbitals have different shapes, energies, and orientations compared to the original atomic orbitals. The geometry and bonding properties of molecules are explained by this hybridization.

When considering the shapes of molecules, the need for hybridization arises. For example, in methane (CH₄), carbon forms four equivalent bonds with hydrogen atoms, arranged tetrahedrally. However, carbon’s ground state electron configuration (1s² 2s² 2p²) suggests that it should form only two bonds. To resolve this, the concept of sp³ hybridization is introduced: one 2s orbital and three 2p orbitals mix to form four equivalent sp³ hybrid orbitals, each forming a sigma bond with a hydrogen atom, resulting in a tetrahedral geometry.

There are various types of hybridization. This classification is based on the number of orbitals and the types of orbitals involved. They are sp hybridization, sp² hybridization, and sp³ hybridization.

Figure 1: Hybridization of Carbon

In sp hybridization, one s orbital and one p orbital combine and hybridize to form two s orbitals. These newly formed sp hybrid orbitals have 50% s character and 50% p character in them. Beryllium chloride is a good example of sp hybridization. sp² hybridization involves one s orbital and two p orbitals, forming three trigonal planar sp² hybrid orbitals. These newly formed hybrid orbitals have 33.33% s character and 66.66% p character. Boron trifluoride is a good example of this. sp³ hybridization is the other type of hybridization where one s orbital and 3p orbitals are involved forming 4 sp³ hybrid orbitals. These hybrid orbitals have 25% s character and 75% p character. Methane is a good example of this type of hybridization.

What is Overlapping

Overlapping describes how atomic orbitals from different atoms interact to form covalent bonds. The extent and manner of this overlap significantly influence the strength and type of the bond formed. When atoms approach each other, their atomic orbitals overlap, and the electrons within these orbitals interact, leading to bond formation.

There are two types of overlapping seen in bond formation, the sigma (σ) bonds and pi (π) bonds. Sigma (σ) bonds are formed by the head-on overlap of orbitals. This can occur between two s orbitals, an s orbital and a p orbital, or two p orbitals aligned end-to-end. Furthermore, these bonds have a cylindrical symmetry around the bond axis, which allows free rotation of the bonded atoms. These bonds are stronger than pi bonds. The reason for this is that they have a greater overlap. An example of a sigma bond is the single bond in a hydrogen molecule (H₂), where two 1s orbitals overlap.

Figure 2: Orbital Overlap for 1s Orbitals of the H2 Atom

Pi bonds are formed by the side-by-side overlap of parallel p orbitals. Pi bonds are typically found in conjunction with a sigma bond in double and triple bonds. The rigidity of the molecule is maintained by the restricted rotation around the bond axis. The overlapping pi bonds are less strong when compared to sigma bonds because the overlapping of p bonds is less intense than sigma bonds. An example is the double bond in ethene (C₂H₄), which consists of one sigma bond and one pi bond.

Similarities Between Hybridization and Overlapping

1. Both are involved in the formation of chemical bonds between atoms.
2. They contribute to the strength of chemical bonds.
3. Moreover, they help in understanding the molecular structure and geometry of molecules.

Difference Between Hybridization and Overlapping

Definition

• Hybridization involves the mixing of atomic orbitals within a single atom to form new, equivalent hybrid orbitals. On the other hand, overlapping describes the physical interaction between atomic orbitals from different atoms when they come close enough to form a covalent bond.

Focus

• Hybridization focuses on the formation of new hybrid orbitals from the atomic orbitals of a single atom, whereas overlapping focuses on the interaction between orbitals from different atoms.

Aim

• While hybridization aims to explain the shapes and bond angles of molecules, overlapping aims to explain how bonds form and the strength of these bonds.

Application

• Hybridization applies primarily to the central atoms in molecules and explains how they form bonds with surrounding atoms. Meanwhile, overlapping applies to the interaction between any pair of atoms forming a bond, not limited to the central atom.

FAQ: Hybridization and Overlapping

1. What is an overlap in chemistry?

• Overlap in chemistry refers to the spatial sharing of electron density between two atomic orbitals, typically resulting in the formation of a chemical bond. This overlap allows electrons to be shared between atoms, which leads to the formation of molecules and the stabilization of chemical structures.

2. What is the difference between hybridization and hybrid orbital?

• Hybridization is the mixing of atomic orbitals to form new hybrid orbitals with different shapes and energies. Hybrid orbitals are the resulting orbitals formed after hybridization, representing the new bonding orbitals that accommodate electron pairs in molecules. Basically, hybridization describes the process, while hybrid orbitals are the outcome.

3. What is the difference between hybridized and unhybridized orbitals?

• Hybridized orbitals result from the mixing of atomic orbitals to form new ones, enabling stronger bonding in molecules. Unhybridized orbitals, however, maintain their original shapes and energies and are not involved in this mixing process.

4. Do unhybridized orbitals overlap?

• Yes, unhybridized orbitals can overlap with each other to form bonds in molecules. For example, in molecules with double or triple bonds, unhybridized p orbitals overlap to create π bonds. This overlapping allows for the sharing of electrons between atoms.

5. How to find hybrid and unhybrid orbitals?

• To find hybrid orbitals, you typically start with the atomic orbitals of the central atom in a molecule or ion. Then, you determine the hybridization by considering the number of sigma bonds and lone pairs around the central atom. For example, if there are four regions of electron density (e.g., four sigma bonds or three sigma bonds and one lone pair), the central atom is sp³ hybridized. Meanwhile, unhybridized orbitals are usually found in atoms that are not involved in hybridization. They retain their original shapes and energies. For example, in a molecule like ethene (C₂H₄), the carbon atoms form sp² hybrid orbitals for bonding with each other, while the unhybridized p orbitals on each carbon atom overlap to form π bonds.

Reference:

1. “Orbital overlap.” Wikipedia. Wikipedia Foundation.
2. “Orbital hybridisation.” Wikipedia. Wikipedia Foundation.

Image Courtesy:

1. “Hybridization of carbon” By Assaiki – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Orbital overlap” By Tem5psu – Own work (CC BY-SA 3.0) via Commons Wikimedia