The students figured out which element they had represented and which element they could bond with, so it is just a matter of putting together the symbols to write the formula. At this point students are only working with elements in the first two periods, so they will be limited to the numbers of compounds they can make. These few examples, however, will help students visualize and manipulate objects to better understand the idea of a covalent bond. The examples we can do easily are the diatomic elements nitrogen, oxygen, and fluorine. This exercise will be difficult for students to discover on their own, so you should have every student in the class work on the same element while you talk them through the procedure.
Procedure Start with fluorine, as it's the easiest to bond with only one shared pair.
Have each student represent a fluorine atom with his or her egg cartons and marbles. Have students pair up so that they have two atoms with them. Ask them to remember the activity with ionic bonding and ask if there's any way to give and take electrons so that both atoms are stable. Hopefully, they will realize that they can't do that. Since these atoms can't give and take electrons to make themselves stable, they are going to have to share the electrons.