Bond order and valence: Analogy between the mayer and the eigenvalue treatments

Mayer's definitions have been applied to calculate bond orders and valence indices in ab initio formalism for some substituted chlorobenzenes. The magnitudes of the quantities so obtained are observed to be in agreement with our expectations from classical concepts. The justification of Mayer's definitions is strengthened by the fact that the values obtained from the eigenvalues of the bond order orbitals (BOOs), the natural hybrid orbitals (NHOs) and the natural bond orbitals (NBOs) coincide with Mayer's values. The bond orders have been used to elucidate the molecular geometries and the free valence indices have been found to be a measure of the reactivity of the different atoms in the molecular environment.