The number of paramagnetic species among the following is ___________.

$\mathrm{B}_{2}, \mathrm{Li}_{2}, \mathrm{C}_{2}, \mathrm{C}_{2}^{-}, \mathrm{O}_{2}^{2-}, \mathrm{O}_{2}^{+}$ and $\mathrm{He}_{2}^{+}$