text: how do i draw an mo energy level diagram for hcccn?   basic mo diagrams only look at one bond at a time, and usually only diatomics.  you'll have to draw one for the cn triple bond, one for the cc single bond and one for the cc triple bond.  it is unlikely that you'll have to do the ch bond, though it can be represented in mo too.  page 24 on this pdf (www.upei.ca/~chem342/resources/ reviews/molecular_orbital_tutorial.pdf)  shows a mo diagram of cn(-).  this will be similar to your case, except one set of lone pairs on the c will be used in the cc single bond...  this is an odd quesion because normally polyatomics are represented using hybridization...