This set consists of sufficient parts to make models of benzene, ethane, ethene and ethyne. These exclusively designed models help to demonstrate both sigma-bonding and pi-bonding and therefore the concept of electron delocalisation and orbital hybridisation. Spheres-2 carbon (6 holes), 8 carbon (5 holes), 2 carbon (4 holes), 18 hydrogen. Link-9 carbon-carbon (ovel shaped) sigma-bonds, 18 carbon-hydrogen (pear shaped) sigma-bonds, 9 pi-bonds (21 pink and 21 purple pieces)