Three-dimensional animations of atoms in the periodic table explain that elements in the same period have the same number of shells (or orbits). A summary of groups in the periodic table is given at the end.

First broadcast:
21 November 2008

This clip could be used to explain that elements in the same period have the same number of shells (or orbits). Ask students to investigate changes to reactivity related to moving down a group and explain in their own words why this changes.