Calcium carbide, CaC₂, contains the acetylide ion, C₂²⁻. Sketch the molecular orbital energy level diagram for the ion and the electron dot structure.
(a) How many net σ and π bonds does the ion have?
(b) What is the carbon–carbon bond order?
(c) Compare the valence bond and MO pictures with regard to the number of σ and π bonds and the bond order.
(d) How has the bond order changed on adding electrons to C₂ to obtain C₂²⁻?
(e) Is the C₂²⁻ ion paramagnetic?