3.2.1.2
Beta-minus decay converts a neutron into a proton
Atomic Structure & Nuclear Stability — AQA A-Level Physics
- Beta-minus ($\beta^{-}$) decay occurs in neutron-rich nuclei.
- A neutron transforms into a proton, emitting an electron and an anti-electron neutrino.
$${}_{Z}^{A}X \longrightarrow {}_{Z+1}^{A}Y + {}_{-1}^{0}\beta + {}_{0}^{0}\bar{\nu}_{e}$$
- Proton number increases by 1.
- Nucleon number stays the same.
- The $\beta^{-}$ particle (electron) is created in the nucleus and ejected — it is not an orbital electron.
Common Mistake
MEDIUM
Students often: Confusing the number of neutrons with the nucleon number in beta decay.
Instead: In $\beta^{-}$ decay, the nucleon number $A$ stays the same. The neutron number decreases by 1 and the proton number increases by 1.
Instead: In $\beta^{-}$ decay, the nucleon number $A$ stays the same. The neutron number decreases by 1 and the proton number increases by 1.