[Siriancook]

My molecular Modeling set has some carbon pieces that only have two or three holes for the bonding links to go. This is weird because I was under the assumption that carbon always needed 4 bonds to be stable. I don’t know what to do with these pieces and also need more carbon pieces in general, so it would be a big help if someone could tell me what they are used for. Thanks

[Babcock_Hall]

There is a difference between the number of bonds and the steric number.  When carbon is sp² hybridized, it bonds to three atoms.  Ethylene (ethene) is a good example.  I am not sure whether or not this explains your model kit.