hybrid orbitals, which are projected towards the six corners of a regular octahedron in SF . These six sp d hybrid orbitals overlap with singly occupied orbitals of fluorine atoms to form six S–F sigma bonds. Thus SF molecule has a regular octahedral geometry as shown in Fig. .
. sp d hybridisation . Molecular Orbital Theory Molecular orbital (MO) theory was developed by F. Hund and R.S.
Mulliken in . The salient features of this theory are : (i) The electrons in a molecule are present in the various molecular orbitals as the electrons of atoms are present in the various atomic orbitals. (ii) The atomic orbitals of comparable energies and proper symmetry combine to form molecular orbitals. (iii) While an electron in an atomic orbital is influenced by one nucleus, in a molecular orbital it is influenced by two or more nuclei depending upon the number of atoms in the molecule.
Thus, Fig. . Octahedral geometry of SF molecule an atomic orbital is monocentric while a molecular orbital is polycentric. (iv) The number of molecular orbital formed is equal to the number of combining atomic orbitals.
When two atomic orbitals combine, two molecular orbitals are formed. One is known as bonding molecular orbital while the other is called antibonding molecular orbital . (v) The bonding molecular orbital has lower energy and hence greater stability than the corresponding antibonding molecular orbital. (vi) Just as the electron probability distribution around a nucleus in an atom is given by an atomic orbital, the electron probability distribution around a group of nuclei in a molecule is given by a molecular orbital.
(vii) The molecular orbitals like atomic orbitals are filled in accordance with the aufbau principle obeying the Pauli’s exclusion principle and the Hund’s rule. . . Formation of Molecular Orbitals Linear Combination of Atomic Orbitals (LCAO) According to wave mechanics, the atomic orbitals can be expressed by wave functions ( ψ ’s) which represent the amplitude of the electron waves.
These are obtained from the solution of Schrödinger wave equation. However, since it cannot