Antoine Henri Becquerel Discovery of Radioactivity U salts cloud film on protected plates Ionized air Could be deflected by B field (unlike X rays) Discovered radioactive decay Antoine Henri Becquerel 1852-1908 Parent Nucleus (Before) Daughter Nucleus (After) Radiation

Types of decay and radiation Effect on Parent A - 4, Z - 2 A - 0, Z + 1 (Conservation of charge) (neutron to proton) A - 0, Z - 1 (proton to neutron) A - 0, Z - 0 Parent loses mass Decay Type  (Alpha) - (Beta-) + (Beta+)  (Gamma) What it is 2p2n (He nuc) (4 cm air) e- (electron) (Thin Al foil, 1-3 m air) e+ (positron) High energy Photon (5 - .05 nm) (some thickness of lead)

21082Pb ______ +   = 2p2n, 4 nucleons, 2 protons 210 - 4 = 206 82 - 2 = 80 Hg (Mercury) 206/80 Hg

4019K ______ + - - = Neutron turns to proton Nucleons remain unchanged Z = 19 + 1 = 20 Ca 40/20 Ca

158O ______ + + + = Proton turns to a neutron Nucleons remain unchanged Z = 8 - 1 = 7 (Nitrogen) 15/7 N

14561Pm ______ +   = 2p2n, 4 nucleons, 2 protons 145 - 4 = 141 61 - 2 = 59 Pr (Praseodymium) 141/59 Praseodymium

6027Co ______ + - - = Neutron turns to proton Nucleons remain unchanged Z = 27 + 1 = 28 Ni 60/28 Ni

4019K ______ + + + = Proton turns to a neutron Nucleons remain unchanged Z = 19 - 1 = 18 Ar 40/18 Ar

22286Rn ______ +   = High energy photon Nucleons remain unchanged Protons remain unchanged 222/86 Rn