Q102 / 180 · AIIMS 2006 · Physics

${ }_{92}^{238} \mathrm{U}$ has 92 protons and 238 nucleons. It decays by emitting an alpha particle and becomes

  • A
    ${ }_{92}^{234} \mathrm{U}$
  • Correct answer
    B
    ${ }_{90}^{234} \mathrm{Th}$
  • C
    $235 \mathrm{U}$
  • D
    ${ }_{93}^{237} \mathrm{~Np}$.

Solution

Emission of alpha particle, decrease the mass number by 4 and charge number by 2 . $\therefore$ Decrease in mass number $=238-4=234$ Decrease in charge number $=92-2=90$ ${ }_{90}^{234} \mathrm{Th}$ is emitted.

Hence, the correct answer is option: 'B'.

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