On emission of a β -particle from the nucleus, the new element formed possesses the same atomic mass but nuclear charge or atomic number is increased by one unit over the parent element following reaction takes place: ‌93239Np
−β
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‌94239Z Number of protons in U−235=92 Product has an atomic number two units less than ‌94239Z and a mass number four units less than ‌94239Z. Hence, Zemits an alpha (α) particle which contain 2 protons and 2 neutrons. ‌94239Z