Two presenters use animations of atoms in the periodic table to explain that elements are arranged according to their size. Mass and atomic numbers are referred to, but not explained. The concept of groups in the periodic table is explained using animations of electrons. The similarity in reactivity of elements in groups is mentioned.

First broadcast:
21 November 2008

This clip could be used as an introduction to the periodic table. Students should gain an understanding that atoms are different sizes and are grouped together due to their structure. It could be followed up by a demonstration of Group 1 metals.