Beta decay involves the emission of an electron. The electron does not come from the electron cloud of the atom, but rather from a neutron in the nucleus that has decayed into a proton and an electron. Electrons are represented by or by . Since a neutron is converted to a proton, the atomic number of the parent has increased by 1, while the atomic mass has remained the same.
Another form of beta decay is positron decay. In this form of fission, a positron, a particle the size and mass of an electron but with a positive charge, is emitted. Positrons are formed when a proton from the nucleus splits into a neutron and a positron. The parent's atomic number has therefore decreased by 1, while its atomic mass has remained the same. Positrons are denoted by the symbol .
Beta particles are less easily shielded but cause less immediate damage than alpha particles.
