Size and mass of atoms

This KS4 resource is a useful introduction to atomic mass leading on to isotopes.

Students are given a small section of the Periodic table and asked to determine the number of protons, neutrons and electrons in three elements and atomic mass.

It moves on to look at chlorine to explain why it has an atomic number 35.5 - so introducing isotopes. There is a plenary activity. 

The answers are included throughout the presentation.