Localized and delocalized Chemical bonding

Localized Chemical Bonding

Localized chemical bonding refers to the formation of covalent bonds between atoms in a molecule, where the shared electron pairs are localized primarily between two atoms. This type of bonding is commonly observed in organic molecules and many inorganic compounds.

In localized chemical bonding, the electrons involved in the bond formation are considered to be localized around the bonding atoms. This means that the electrons are more likely to be found in the region between the bonded atoms, and their distribution is not spread out over the entire molecule.

The concept of localized chemical bonding is often described using Lewis structures or electron dot structures. In Lewis structures, valence electrons are represented as dots or lines around the atomic symbols, indicating the sharing or transfer of electrons between atoms to form bonds.

Example of localized bond:

In a molecule like methane (CH4), the four covalent bonds between the carbon atom and the four hydrogen atoms are localized. Each hydrogen atom contributes one electron, and the carbon atom contributes four electrons to form the covalent bonds. The shared electrons are localized between the carbon and hydrogen atoms, giving rise to the tetrahedral geometry of the molecule.
Localized bonding is also observed in double and triple bonds, where two or three pairs of electrons are shared between two atoms. For instance, in ethene (C2H4), a double bond forms between two carbon atoms, with two pairs of electrons shared between them. The remaining bonds with hydrogen atoms are also localized.
It is important to note that while localized bonding is a useful concept to understand the basic principles of chemical bonding, it is a simplified representation. In reality, the electron density in a molecule is distributed over a larger region, and the concept of localized bonding becomes less accurate in more complex molecules or under certain conditions.

Delocalized Chemical Bonding:

Delocalized chemical bonding refers to bonding in certain molecules or materials where electrons are not confined to a specific bond between two atoms. Instead, the electrons are shared or spread out over a larger region or multiple atoms within the molecule or material. This results in the formation of electron clouds or "delocalized" electron systems.

Example of Delocalized Bond:

One common example of delocalized bonding is found in molecules with conjugated systems, such as in organic compounds like benzene. The six carbon atoms in benzene form a ring, and each carbon atom is bonded to one hydrogen atom. However, the bonding within the ring is not localized between each pair of adjacent carbon atoms but rather involves a delocalized ring of π (pi) electrons that are spread out over the entire molecule. This delocalization of electrons results in the stability and unique properties of benzene.
Another example of delocalized bonding can be found in metallic bonding. 

In metals, the valence electrons are not tightly associated with any particular atom but are free to move throughout the crystal lattice. This delocalization of electrons gives rise to the characteristic properties of metals, such as high electrical and thermal conductivity.

Delocalized bonding can also occur in materials like polymers, where long chains of atoms are connected by alternating single and double bonds. The double bonds’ π (pi) electrons are delocalized over the entire polymer chain, allowing for enhanced stability and unique electrical properties.

Overall, delocalized chemical bonding plays a crucial role in determining the properties and behavior of many molecules and materials. It contributes to the stability, conductivity, and other characteristic features exhibited by these substances.