Give features of Molecular Orbital $(MO)$ theory:

(N/A) Molecular Orbital $(MO)$ theory was developed by $F. Hund$ and $R.S. Mulliken$ in $1932$. The features of this theory are as follows:
$(i)$ The electrons in a molecule are present in various molecular orbitals,just as electrons in atoms are present in various atomic orbitals.
$(ii)$ 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,an atomic orbital is monocentric,while a molecular orbital is polycentric.
$(iv)$ The number of molecular orbitals formed is equal to the number of combining atomic orbitals. When two atomic orbitals combine,two molecular orbitals are formed: one is known as a bonding molecular orbital,and the other is called an 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.
$(vii)$ Molecular orbitals,like atomic orbitals,are filled in accordance with the $Aufbau$ principle,obeying the $Pauli$ exclusion principle and $Hund$'s rule.