This is a Challenge for the beginning of an Inorganic class, to remind students of the basics of Aufbau, etc. Inorganic Challenges are exercises designed to be solved by a small group of students. Some Challenges practice a problem-solving algorithm, some reinforce important concepts, and some involve creativity or games. You can pick and choose Challenges from our Web site to increase active learning in your classroom, and we ask that you contribute creative Challenges of your own to give a head start to teachers at other colleges and universities! Please visit http://chem.rochester.edu/~plhgrp/iicf/subjects.htm