I won't construct the complete orbital diagrams here, but what I mainly want to do, is to try to use this diagram to understand, why is the acetylate anion more stable then the vinyl anium, for the vinyl anium we know that carbon is sp2 hybridized and so this sp2 hybrid none-bonding orbital will lye 2 3rds of the way between the 2s and the 2p levels that are negatively charged. 