Draw the MO diagram for acetylide ion `C_(2)^(2-)` and calculate its bond order.

Explanation

Acetylide ion, `C_(2)^(2-)` in acetylene: `underset(1s^(2)" "2s^(2)" "2p^(4))(C)rarrunderset(1s^(2)" "2s^(2)" "2p^(2))(C^(2-)+2e)`
Electronic configuration of `C_(2)^(2-)` ion is : `sigma 1s^(2) sigma **1s^(2)sigma1s^(2) pi2p_(x)^(2)pi2p_(y)^(2)`

Bond order `= (N_(b)-N_(a))/(2)=(8-4)/(2)=2`