The answer is <span>the atomic number and the mass number will decrease.
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When atoms undergo radioactive decay, alpha particles release.
→ 
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When atoms undergo radioactive decay, alpha particles release.
Alpha particles consist of two protons and two neutrons. So, mass is 4 (2+2) amu<span>.
When an atom of emits an alpha particle, its atomic number will be reduced by 2 and a mass number will be reduced by 4:</span>
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