ABSTRACT
However, once an electron has been acquired, it is easy for additional electrons to add to this structure, and further reduction occurs spontaneously through the activated oxygen species. It follows from the molecular orbital method that an oxygen molecule may be represented as per the autbau principle of filling atomic orbitals. When oxygen molecules are formed from two oxygen atoms, it does not matter if their molecular orbitals differ significantly. Each pair of oxygen atomic orbitals so combined must give rise to a pair of new molecular orbitals. The energetic sequence of molecular orbitals for homonuclear diatomic molecules like oxygen has been suggested by Mulliken, according to whom two homonuclear atoms are to be brought up to one another. In the biological system, the inspired dioxygen of air undergoes reduction into various intermediate oxygen species in aqueous biomedia.
