When an α - particle emits from a radioactive nuclei, then its mass number is decreased by 4 unit and atomic number is decreased by 2 unit. When a β-particle emits from a radioactive nuclei, then its mass number is unaffected, whereas atomic number is increased by one unit. Here, initial nuclei =‌92U235 Final nuclei =‌82P203 Change in mass number =235−203=32 Number of α-particle emitted =‌
32
4
=8 ∴ Number of emitted β-particles =8×2−(92−82)=16−10=6