Which of the following species has lowest ionization potential? Give explanation.(1) O22-(2) O2(3) O2+(4) O2-

peroxide that is o2^2-
Electronic configurations:
Molecular oxygen, O₂ . (σ2s)²(σ2s*)²(σ2p)²(π2p)⁴(π2p*)² . . 2 unpaired electrons in the two π* orbitals
Superoxide Ion, O₂⁻ . (σ2s)²(σ2s*)²(σ2p)²(π2p)⁴(π2p*)³ . . 3 electrons (1 unpaired) in the two π* orbitals
Peroxide Ion, O₂²⁻ . . (σ2s)²(σ2s*)²(σ2p)²(π2p)⁴(π2p*)⁴ . . 4 electrons (all paired) in the two π* orbitals

electrons in non-bonding orbitals tend to be in deep orbitals (nearlyatomic orbitals) associated almost entirely with one nucleus or the other, and thus they spend equal time within as they do between nuclei. These electrons neither contribute to nor detract from bond strength and thus are best described as lone pairs.
so more electron in lone pair it is easier for the molecule to remove such electron