Fission is a possible consequence of this instability only in U-235 and other fissile material. Alpha particles are very massive in comparison with the other types of radioactive particles below. Within a few centimetres of travelling through the air the alpha particle will collide with the air molecules, lose kinetic energy in the collisions, pick up electrons and become a neutral stable helium atom. Alpha particles cannot penetrate skin, although enough exposure will cause a severe skin burn. The particle also emits gamma radiation which sheds excess energy leaving a more stable isotope.
Beta particles arise from the decay of a neutron.
It did not exist before decay occurred. Each isotope gives off its own unique characteristic beta energy. Only the highest energy can penetrate skin. Since most of our radiation detectors depend on collisions between radiation particles and a gas, antineutrinos where only isolated very recently. Gamma radiation, symbol '' Gamma radiation is high energy photons of the electromagnetic spectrum and usually accompanies and .