2. Summary of Properties intensity decreases by 10% by 3 cm of lead stopped by 12 cm of air or several mm of paper stopped by 4 cm of air or a sheet of paper penetrating ability 1 u 0 0 4 u mass 0 0 1- 2+ charge 1 0 n high energy radiation 0 -1 e electron 4 2 He nucleus nature of radiation neutron (n) Gamma ( Ϫ ) Beta ( β ) Alpha ( α ) Property