My advanced inorganic students often have trouble conceptualizing microstates and term symbols. This exercise is intended to provide a hands-on assembly of microstate models and their combination to form term symbols.

Trays are constructed to represent individual microstates - for p-electrons a tray contains 6 boxes to represent the two m_s values corresponding to each of the three m_l values. Balls are placed in the boxes to represent a given microstate - one tray for each possible microstate of the desired pⁿ configuration. Once all of the microstate trays have been constructed, they are grouped to form the term symbols.

I used 126-count silicone candy molds to create the trays - they can easily be cut to give twenty-one 2 x 3 trays. The exercise as written requires 20 trays per group of students. Any type of ball or marble or anything else that is appropriately sized to fit into the molds can be used to represent electrons. 

The students were divided into groups and each group given enough trays and balls to create the microstate models. After the groups were finished with the p² models, we discussed them as a class. They then worked on the p³ models.