Using mo theory, predict which of the following species has the longest bond and which the strongest bond, respectively: o2, o2−, o22−

MO theory stands for Molecular Orbital theory which is sued to detremine the molecule structure. The bond length in the oxygen species, O2+, O2, O2-, O2^(2-), can be explained by the positions of the electrons in this theory. 
bond order = 1/2 (#e- in bonding MO's - #e- in antibonding MO's) 
bond order for O2 is 2 
bond order for O2+ is 2.5
bond order for O2- is 1.5
bond order for O2(2-) is 1

Ur e n d is not real