How does alpha decay affect the mass number of a nucleus how does beta decay affect the mass number?

When an alpha particle is emitted from a nucleus the nucleus loses two protons and two neutrons. This means the atomic mass number decreases by 4 and the atomic number decreases by 2. The electron is ejected from the nucleus and is called the beta particle. The proton stays in the nucleus and changes the identity of the atom, to the next higher atomic number.