Bond order in He₂ species is

He₂(4e^-)

Molecular orbital configuration is, $\sigma 1s^2{\sigma }^{*}1s^2$

Bond order=$\frac{{\mathrm{N}}_{\mathrm{b}}-{\mathrm{N}}_{\mathrm{a}}}{2}=\frac{2-2}{2}=0$

where, N_b= no. of bonding electrons , N_a= no. of antibonding electrons.