The bond order and magnetic behaviour of O2- ion are, respectively:

🧠 $\ce{O2-}$ (superoxide ion) has 17 electrons. Apply MO theory.

$\ce{O2}$ has 16e and BO = 2. Adding one electron goes into the antibonding $\pi^*_{2p}$ orbital:

$\ce{O2-}$: ...\pi_{2p}^4\pi^*_{2p}^3

$\text{BO} = \frac{\text{bonding} - \text{antibonding}}{2} = \frac{10 - 7}{2} = 1.5$

The $\pi^*_{2p}$ level now has 3 electrons across 2 degenerate orbitals → one orbital is full (2e), one has 1e → 1 unpaired electron → paramagnetic.

⚡ Rule of thumb: $\ce{O2}$ species BO: $\ce{O2+}$(2.5) → $\ce{O2}$(2) → $\ce{O2-}$(1.5) → $\ce{O2^{2-}}$(1). Each added electron reduces BO by 0.5.

$\boxed{\text{Answer: (b) 1.5 and paramagnetic}}$