Molecular orbital diagram
…first excited state has both HOMO electrons paired in one orbital with opposite spins, and is known as singlet oxygen. The bond order decreases and the bond length increases in the order O+ 2 (112.2 pm), O 2 (121 pm), O− 2 (128 pm) and O2− 2 (149 pm). In difluorine two additional electrons occupy the 2pπ* with a…