Alpha decay happens when a radioactive particle decays into an alpha particle (helium-4 nucleus) and a new particle. The new particle has an atomic number that is two less than the original radioactive particle and an atomic mass equal to four less than the original particle.Continue Reading
A radioactive material of atomic number A and atomic mass B will decay into an alpha particle and a new particle with an atomic number two less than A, and an atomic mass four less than B.
Alpha particles and helium-4 nuclei are the same; they have an atomic number of two and an atomic mass of four. When a radioactive material decays, it loses two protons and two neutrons, so it becomes a new particle.
One isotope of thorium is thorium-232, which has an atomic mass of 232 and an atomic number of 90. This isotope will decay into an alpha particle and radium-228, with atomic number 88 and atomic mass 228.Learn more about Chemical Equations