Which of the following species is not paramagnetic?

The $\sigma _{2s}^*$ molecular orbital has a nodal plane similar to which of the following orbitals?

The correct sequence of bond order is

Consider the following statements.
$I$. In the conversion of $O_2$ to $O_2^{2+}$,bond order decreases.
$II$. In the conversion of $O_2$ to $O_2^{2+}$,magnetic property is not changed.
$III$. In the conversion of $O_2$ to $O_2^{2+}$,bond length decreases.
$IV$. $O_2^{2-}$ and $B_2$ have same bond order.
Identify the correct statements.

In which of the following ionization processes,the bond order has increased and the magnetic behaviour has changed?

Which of the following has the least bond energy?