The term 2ψ 1ψ 2 arises due to overlapping and fusion of atomic orbitals. Since the probability of finding the electron in a particular region of space around the nucleus is given by the square of the wave function. By Subtraction of Wave Functions- When two waves are out of phase, they are subtracted from each other so that the amplitude of the new wave is.By Addition of wave functions- When the two waves are in phase so that they add up and the amplitude of the new wave is.When these atoms form a bond, the electrons originally present in atomic orbitals now occupy molecular orbitals which is formed by a linear combination of atomic orbitals ψ 1 and ψ 2 in two ways. Consider two similar atoms 1 and 2 with atomic orbitals described by the wave functions ψ1 and ψ2. For convenience, a new approximate method known as Linear Combination of Atomic Orbitals ( LCAO) is used to obtain wave functions for molecular orbitals. According to the modern concept, Z-axis is taken as an internuclear axis.įormation of Molecular Orbitals (LCAO Method):ĭue to the complex nature of the Schrodinger wave equation, it is not easy to solve it for molecules. However, they can overlap along Z-axis because both have the same symmetry about Z-axis. Example- 2s and 2px orbitals can overlap along X-axis but 2s and 2pz cannot overlap. Symmetry about the Molecular Axis- The combining atomic orbitals should have the same symmetry about the molecular axis (i.e.Thus, greater is the overlap of atomic orbitals, greater is the build-up of charge between the nuclei causing greater attraction and thus will form a stronger bond. This overlap brings the electron cloud in between the two nuclei and minimizes repulsion between them. Extent of Overlapping- The atomic orbitals can combine only if they can overlap to a considerable extent.In heteronuclear diatomic molecules of the type AB, such combinations may be possible. Thus, 1s and 2s or 2s and 2p orbitals of two atoms of the same element will not combine to form molecular orbitals in homonuclear diatomic molecules of type A 2. Energy of the Combining Atomic Orbitals- The energies of the combining atomic orbitals should not differ much from one another.

Important Conditions Required by Atomic Orbitals To Form Molecular Orbitals:Ītomic orbitals can combine to form molecular orbitals only if the following conditions are satisfied. i.e., the electron is moving in the field of more than one nucleus. Thus, a molecular orbital is polycentric. When two atomic orbitals overlap, they lose their identity and form new orbitals known as Molecular orbitals which is defined as “the region in space defined by its size and shape associated with two or more atoms in a molecule and having a capacity of two electrons. Formation of Molecular Orbitals (LCAO Method):.Important Conditions Required by Atomic Orbitals To Form Molecular Orbitals:.

In phase combination of atomic orbitals