# Question #0fd26

Actually, the atomic number increases by one in a beta decay, also known as a ${\beta}^{-} \text{decay}$, because a neutron from the nucleus emits an electron with high kinetic energy, also called a $\beta \text{-particle}$, and an antineutriono, leaving behind a proton.
The atomic number would decrease by one in a ${\beta}^{+} \text{decay}$, which is commonly called positron decay, because this time a proton will be converted into a neutron with the emission of a neutrino and a positron.
Similar to a ${\beta}^{-} \text{decay}$, the positron decay will leave the mass number unchanged.