Maths, Physics Revision Physicss Maths Physics Physics A Level Physics Home Maths Maths Revision hut Radioactivity 226 88 Ra 222 86 Rn 4 2 α (note. the top number is the atomic mass  (protons + neutrons) and  the bottom number is the atomic number ( number of protons)) Beta Decay β Some elements decay by emitting beta  particles. This  is when a neutron changes to proton and an electron. The proton stays in the nucleus but the electron is emitted as  a beta particle. Carbon 14 decays to  Nitrogen by beta  emission. 14 6 C 14 7 N 0 -1 β Gamma emission γ After alpha or beta particles have been emitted the  nucleus can remain in an “exited state. The protons and neutrons are rearranged resulting in γ emission. Gamma emission is not in the form of particles, it is  high energy electomagnetic radiation.