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NDA 2022 GAT · General Knowledge · Nuclear and Modern Physics · hard

An atom of uranium-238 (atomic number 92) emits one alpha particle. The resulting nucleus has

Single correct option

An atom of uranium-238 (atomic number 92) emits one alpha particle. The resulting nucleus has
  1. A. mass number 234 and atomic number 91
  2. B. mass number 234 and atomic number 90
  3. C. mass number 238 and atomic number 93
  4. D. mass number 236 and atomic number 90
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Answer: (B) mass number 234 and atomic number 90

An alpha particle is a helium nucleus with 2 protons and 2 neutrons, so mass number falls by 4 and atomic number by 2. The product has mass number 234 and atomic number 90, which is thorium-234. A beta emission would raise the atomic number by one instead.
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Original question written in the NDA 2022 GAT pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake