The main difference between localized and delocalized bonds is that localized bonding involves sharing electrons between two atoms. In contrast, delocalized bonding involves spreading electrons over a larger molecular structure or multiple atoms.
Localized and delocalized bonds are fundamental concepts in chemistry that describe the distribution of electrons in chemical bonds. Therefore, understanding the nature of these bonds is essential for comprehending molecules’ structure, stability, reactivity, and properties.
Key Areas Covered
1. What is a Localized Bond
– Definition, Features, Example
2. What is a Delocalized Bond
– Definition, Features, Example
3. Similarities Between Localized and Delocalized Bond
– Outline of Common Features
4. Difference Between Localized and Delocalized Bond
– Comparison of Key Differences
Key Terms
Localized Bond, Delocalized Bond
What is a Localized Bond
Localized bonding refers to sharing electron pairs between two atoms in a molecule. It is a fundamental concept in chemistry that helps explain the formation and stability of covalent bonds. In this context, electrons are considered localized or confined to the region between the bonded atoms. When two atoms come together to form a covalent bond, they share electrons to achieve a more stable electron configuration. The electrons involved in the bond are typically derived from overlapping atomic orbitals. The most common example is the sharing of electron pairs between nonmetal atoms.
Example of Localized Bonding
Let’s take the example of hydrogen chloride (HCl) to illustrate localized bonding. Hydrogen has one valence electron, and chlorine has seven. To attain a stable electron configuration, hydrogen needs one more electron, while chlorine needs one electron to complete its octet. When a hydrogen atom approaches a chlorine atom, their atomic orbitals overlap, allowing the two electrons to be shared between the atoms. This sharing forms a localized bond, where the electron pair spends most of its time between the hydrogen and chlorine nuclei.
Localized bonding can be further understood by considering the concept of molecular orbitals. In the case of hydrogen chloride, the bonding molecular orbital is formed by the constructive overlap of the hydrogen 1s orbital and the chlorine 3p orbital. This results in forming a sigma bond, a localized bond with electron density concentrated between the two nuclei. Moreover, the electrons in the Sigma bond are considered to be owned by the hydrogen and chlorine atoms involved in the bond.
Localized bonding is a critical factor in determining a molecule’s properties and reactivity, influenced by factors such as electronegativity, orbital overlap, and the presence of lone pairs. It creates strong and stable bonds between atoms, with electronegativity differences and significant orbital overlap contributing to their strength. Lone pairs of electrons play a role in shaping the molecule and its reactivity.
However, not all bonds are localized. Delocalized bonding occurs when electrons are spread over a larger region or multiple atoms, commonly observed in molecules with conjugated systems or resonance structures. This concept expands our understanding of bonding beyond localized interactions.
What is a Delocalized Bond
Delocalized bonding occurs when electrons are not confined to the region between two specific atoms but are spread out over multiple atoms or regions within a molecule. This phenomenon arises from the concept of electron delocalization, wherein electrons have the freedom to move through a larger portion of the molecule, resulting in unique bonding properties and behaviors.
One classic example of delocalized bonding is found in the benzene molecule. Benzene consists of a ring of six carbon atoms, with each carbon atom bonded to one hydrogen atom and one adjacent carbon atom. The key feature of benzene lies in its alternating double and single bonds between the carbon atoms. However, these alternating bonds do not imply fixed positions for the electrons involved. Instead, the π-electrons in the p-orbitals of the carbon atoms undergo delocalization, freely moving throughout the entire ring. This delocalized electron cloud gives rise to the exceptional stability and aromatic properties exhibited by benzene.
Delocalized bonding extends beyond organic compounds and encompasses inorganic and coordination compounds, as well as various functional groups. Examples include carbonyls, conjugated systems, and even inorganic ions like the nitrate ion (NO3^-). Delocalized bonding significantly impacts molecular structure, stability, reactivity, and optical properties. It enhances stability by spreading electron density, reduces electron-electron repulsion, and influences charge distribution. Furthermore, delocalized bonding affects acidity and basicity in organic compounds, and in certain compounds like dyes and pigments, it enables the absorption and emission of specific light wavelengths, resulting in vibrant colors. Thus, these characteristics find practical applications in industries such as textiles, displays, and solar cells.
Similarities Between Localized and Delocalized Bond
- Localized and delocalized bonds involve the sharing of electrons between atoms.
- Both localized and delocalized bonds can be covalent in nature.
- Moreover, these types of bonds contribute to the stability of molecules.
- Both localized and delocalized bonds can be represented using Lewis structures or molecular orbital diagrams.
Difference Between Localized and Delocalized Bond
Definition
A localized bond refers to a covalent bond formed between two atoms, with the electron density primarily concentrated between the bonded atoms, while a delocalized bond refers to a bond in which electron density is spread over multiple atoms or a larger region rather than being confined to a specific bond between two atoms.
Electrons
In localized bonding, electrons are confined to a specific region between two atoms, forming a distinct bond, while in delocalized bonding, electrons are not confined to a specific region between two atoms but are instead spread out over multiple atoms or a larger region of the molecule.
Found in
Localized bonds are typically found in covalent compounds, where electrons are shared between two atoms to form a bond, whereas delocalized bonds are commonly found in molecules with extended pi systems or resonance structures.
Electron Distribution
In localized bonds, electrons are associated with specific atom pairs and are not free to move throughout the molecule. In delocalized bonds, electrons are not confined to specific atom pairs but are shared among multiple atoms or regions.
Bond Length
Localized bonds have a well-defined bond length determined by the distance between the participating atoms, whereas delocalized bonds may not have a specific bond length since the electrons are distributed over a larger area.
Conclusion
The main difference between localized and delocalized bonds is that localized bonding involves the sharing of electrons between two atoms, whereas delocalized bonding involves the spreading of electrons over a larger molecular structure or multiple atoms.
Reference:
1. “Delocalized Electron.” Byju’s.
2. “Localized Bonding.” Libre Texts – Chemistry.
Image Courtesy:
1. “HCl molecule model-VdW surface” By Bobarino – This W3C-unspecified vector image was created with Inkscape (CC BY-SA 3.0) via Commons Wikimedia
2. “Delocalized bonding” By Alsosaid1987 – Own work (CC BY-SA 4.0) via Commons Wikimedia
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