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Sir, Please clearly explain about the concept of antibonding orbital, how to find it. And how to find out the bondorder

Sir,
Please clearly explain about the concept of antibonding orbital, how to find it. And how to find out the bondorder

Grade:12

1 Answers

Aarti Gupta
askIITians Faculty 300 Points
10 years ago

Antibonding molecular orbitals (MOs) are normally higher in energy than bonding MOs. Bonding and antibonding orbitals form when atoms combine into molecules as a result of the Pauli exclusion principle. Consider two hydrogen atoms that are initially far apart and are brought together. When they are far apart and isolated, the atoms have identical energy levels. However, as the spacing between the two atoms becomes smaller, the electron wave functions begin to overlap. The Pauli principle dictates that no two electrons in an interacting system may have the same quantum state. Therefore, each energy level of the isolated atoms splits into two molecular orbitals belonging to the pair, one lower in energy than the original atomic level and one higher. For example, the ground state energy level, 1s, splits into two molecular orbitals. Since the lower orbital is lower in energy than the original atomic orbitals of the separate atoms, it is more stable, and promotes the bonding of the two H atoms into H2. This is the bonding orbital. The higher orbital is higher in energy than the original atomic orbitals and is less stable, and therefore opposes the bonding. This is the antibonding orbital. In a molecule such as H2, the two electrons normally occupy the bonding orbital, since it is lower in energy, and therefore the molecule is more stable than the separate H atoms.

A molecular orbital becomes antibonding when there is less electron density between the two nuclei than there would be if there were no bonding interaction at all. When an MO changes sign (from positive to negative) at a nodal plane between two atoms, it is said to be antibonding with respect to those atoms. Antibonding orbitals are often labelled with an asterisk (*) on molecular orbital diagrams.

For bond order to calculate :-
Bond order = 1/2 (bonding electrons - antibonding electrons)
Thanks & regards
Aarti Gupta
askiitians Faculty

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