If Boris is already using Moodle to disseminate lecture notes, lab forms and to answer student questions outside of class time vis a discussion forum, then it makes sense for him to take advantage of Moodle’s quiz feature to help students with the Periodic Table.

Boris could take the areas he finds students are specifically having difficulty with, and create a quiz with questions that will help students understand the Periodic Table better, and could also provide them with feedback on whether or not they are on the right track.

I also feel like Boris should not be re-inventing the wheel on this, if he is finding his students are struggling with the Periodic Table, probably students in other Chemistry classes are also struggling, so perhaps he could get together with his colleagues and together they can come up with questions for a quiz to help students gain a better understanding. Boris should also check online, as the Periodic Table has been around forever, and I am sure there are teachers who have already created something like this that Boris can copy or learn from.