This pack of blue atoms are used typically to represent nitrogen atoms and is for extending your existing set or for replacing lost atoms. Each pack contains 10 balls with three holes in each ball in a trigonal planar (120°) array. Each atom is 23 mm diameter.
Why would I need these? You could use them to represent a trigonal nitrogen atom in a compound such as pyridine or an amide.
The Molymod® system is the original, unique, dual-scale system of high quality low-cost molecular models. These enormously popular sets are ideal for students but are also used by scientists all over the world.