An alpha particle is identical to
- A. a helium nucleus, two protons and two neutrons
- B. a fast electron
- C. a photon
- D. a proton
Explanation
Alpha emission therefore reduces the mass number by 4 and the atomic number by 2, moving the element two places back in the periodic table. Being heavy and doubly charged, alpha particles ionise strongly but are stopped by a sheet of paper or a few centimetres of air. A fast electron is a beta particle.