Practice question

Alpha decay ejects a helium-4 nucleus containing two protons and two neutrons. Parent nucleus therefore loses atomic number by two, shifting element position in periodic table, and mass number by four, reflecting loss of four nucleons. This contrasts with beta decay, where mass number remains unchanged and atomic number changes by one, and gamma decay where neither changes. Alpha emission is common in heavy unstable nuclei seeking stability and produces daughter nuclei with significantly lower mass, readily identifiable by alpha spectroscopy and mass balance.