The number of unpaired electrons in $O_2$ molecule is

Identify the set containing isoelectronic species.

Which of the following is paramagnetic and contains a three-electron bond in its structure?

Arrange the following in the increasing order of their bond dissociation energy: $O_2$,$O_2^+$,$O_2^-$,and $O_2^{2-}$.

Among the following molecules / ions $C_2^{2-}, N_2^{2-}, O_2^{2-}, O_2$,which one is diamagnetic and has the shortest bond length?

The molecular orbital configuration of a diatomic molecule is
$\sigma 1s^2 \sigma^* 1s^2 \sigma 2s^2 \sigma^* 2s^2 \sigma 2p_x^2 \pi 2p_y^2 \pi 2p_z^2$
Its bond order is