For the species o2, o2+, o2-, give the electron configuration and the bond order for each. which has the
strongest bond?

The electron configuration of the oxygen molecule must accommodate 16 electrons. The way bond order is determined is through the equation: 

bond order = 1/2 (#e- in bonding MO's - #e- in antibonding MO's) 

σ1s and σ*1s represent the bonding and antibonding orbitals of the 1s level. 
σ2s and σ*2s represent the bonding and antibonding orbitals of the 2s level. 
σ2p and σ*2p represent the bonding and antibonding orbitrals of the 2px orbitals due to an end-on orientation of the atomic orbitals. 
π2p and π*2p molecular orbitals originate from the 2py and 2pz atomic orbitals of the two oxygen atoms. 

The electron configurations are shown below where we have 16 electrons to account for in O2. 
The bond order decreases and the bond length increases in the order O2+ (112.2 pm), O2 (121 pm), O2- (128 pm) and O22- (149 pm). 

σ1s(2) σ*1s(2) σ2s(2) σ*2s(2) σ2p(2) π2py(2) π*2py(2) π2py(1) π*2py(1) σ*2p(0) 
From the equation above the bond order for O2 is 2 

σ1s(2) σ*1s(2) σ2s(2) σ*2s(2) σ2p(2) π2py(2) π2py(2) π2*py(1) π*2py(0) σ*2p(0) 
From the equation above the bond order for O2+ is 2.5 

σ1s(2) σ*1s(2) σ2s(2) σ*2s(2) σ2p(2) π2py(2) π*2py(2) π2py(2) π*2py(1) σ*2p(0) 
From the equation above the bond order for O2(-) is 1.5 

σ1s(2) σ*1s(2) σ2s(2) σ*2s(2) σ2p(2) π2py(2) π*2py(2) π2py(1) π*2py(1) σ*2p(0) 
From the equation above the bond order for O2(2-) is 1