Answer is: no change in mass and adding a proton to the nucleus .
Beta
decay is radioactive decay in which
a beta ray and a neutrino are emitted from an atomic
nucleus.
There are two types of beta
decay: beta minus and beta
plus.
In beta minus decay, neutron is converted to a
proton and an electron and
an electron antineutrino.
In beta
plus decay, a proton is converted to a neutron and positron and an electron neutrino, so mass number does not change.
