1. The problem statement, all variables and given/known data http://i.imgur.com/HunOeH0.png 2. Relevant equations MO model 3. The attempt at a solution as far as i know, number of pi bond is equal to 3 - the "power" of p (the hybridized bond formed) the answer "4" is only calculated from the 4 elements' bond in part b, so why the central O and C atom is not considered with calculation of pi bond? Thanks!