4.Chemical Bonding and Molecular Structure
hard

Give difference : Bonding molecular orbital and antibonding molecular orbitals.

Option A
Option B
Option C
Option D

Solution

Bonding Molecular Orbitals ($BMO$)

Antibonding Molecular Orbitals ($ABMO$)

It is in short $BMO$. Its wave function is express by $\psi_{\text {MO }}$.

It is in short $ABMO$ its wave function is express by $\psi_{\text {MO }}^{*}$

Definition: They are formed by the addition of atomic orbital is known of $BMO$.

$\psi_{\mathrm{MO}}=\psi_{\mathrm{A}}+\psi_{\mathrm{B}}$

Definition : They are formed by the substractive effect of the atomic orbitals is known $ABMO.$

Qualitative, the formation of $BMO$ can be understood in terms of the constructive of the electron waves of the combining atoms and reinforce each other.

$\psi^{*}$ MO $=\psi_{\text {A }}$ – $\psi_{\text {B }}$ Qualitative, the formation of $ABMO$ can be under- stood in terms of the destructive interference of the electron waves of the combining atoms and cancel each other.

As a result, the electron density in a $BMO$ is located between the nuclei of the bonded atoms because of which the repulsing between the nuclei is very less.

In case of an $ABMO$, most of the electron density is located away from the space between the nuclei

 

The nodal plane is not present in $BMO.$

There is a nodal plane (on which electron density is zero) between the nuclei.

Electron placed in a $BMO$ tend to hold the nuclei together and stabilize a molecule. The electron placed in the $ABMO$ destabilize the molecule.
A $BMO$ always possesses lower energy than either the atomic orbitals that have combined to from it. The $ABMO$ always possesses higher of energy than either of the atomic orbitals that have combined to form it
In $BMO$, the repulsion between electron-electron is less than the attraction between electron and nuclei, So energy is less of $BMO$. In$ABMO$, repulsion of electron is more than the attraction between the electrons and the nuclei, which causes a not increase energy.
BMO is stable. e.g. $\sigma$ and $\pi$ are $BMO$. $\mathrm{ABMO}$ is unstable. e.g. $\sigma^{*}$ and $\pi^{*}$ are $ABMO$.

 

Standard 11
Chemistry

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