During alpha decay the nucleus of the atom expels 2 protons and 2 neutrons. Alpha decay reduces the size of the nucleus. An atom of a new element is formed which has a mass number reduced by 4 and an atomic number reduced by 2. In beta decay a neutron breaks apart to form a proton and an electron. The proton remains in the nucleus and the electron is expelled as a beta particle.
Beta decay decreases the neutron to proton ratio.
An atom of a new element is formed which has an atomic number increased by 1. There is no change in mass. Emission of a high energy gamma ray during gamma decay reduces the energy of an unstable nucleus. Neither the atomic number or mass change. Electron capture by a proton changes the proton to a neutron.