According to question, Initial nuclei =92238U Final nuclei =82206Pb Change in atomic number =92−82=10 When an α - particle emits from a nuclei, then its atomic number is decreased by 2 units and atomic mass is decreased by 4 units. When a β -particle emits from a nuclei, then atomic number of parent nuclei is increased by 1 unit whereas its atomic mass remains same. Change in atomic mass =238−206=32 Since, atomic mass changes only due to emission α -particle, hence number of emitted α -particle =
32
4
=8 Number of emitted β -particles = total change in atomic number due to emission of α -particles total change in atomic number =8×2−10=6