(a) MO configuration of O2+(8+8−1=15)=σ1s2,σ∗1s2,σ2s2,σ∗2s2,σ2pz2,π2px2≈π2py2,π2px1≈π2py0BO=2Nb−Na (where, Nb= number of electrons in bonding molecular orbital Na= number of electrons in anti-bonding molecular orbital ∴BO=210−5=2.5 Similarly, (b) O2−(8+8+1=17) so BO=2Nb−Na=210−7=1.5 (c) O22−(8+8+2=18) BO=2Nb−Na=210−8=1 (d) O2(8+8=16) BO=210−6=2 Thus, O2−shows the bond order 1.5.