There are 5 different types of radioactive decay. B is the daughter isotope or the isotope formed. Alpha decay is is not very penetrating because the He atoms capture electrons before traveling very far. However it is very damaging because the alpha particles can knock atoms off of molecules .Alpha decay is the most common in elements with an atomic number greater than 83. Beta negative decay is more penetrating than alpha decay because the particles are smaller, but less penetrating than gamma decay.
Beta decay is most common in elements with a high neutron to proton ratio.
A very highly charged gamma ray is given off when the parent isotope falls into a lower energy state. Gamma radiation is the most penetrating of all. These photons can pass through the body and cause damage by ionizing all the molecules in their way. A positron is exactly like an electron in mass and charge force except with a positive charge. It is formed when a proton breaks into a neutron with mass and no charge and this positron with no mass and the positive charge.