Question

The compound unstable nucleus ${ }_{92}^{236} U$ often decays in accordance with the following reaction ${ }_{92}^{236} U \rightarrow{ }_{54}^{140} Xe +{ }_{38}^{94} Sr +$ other particles In the nuclear reaction presented above, the "other particle" might be

• A. an alpha particle, which consists of two protons and two neutrons
• B. two protons
• C. one proton and one neutron
• D. two neutrons

Answer 1

Answer: (D)

Nuclear reactions conserve total charge, and also conserve the total approximate mass. The other particles in the reaction will have mass
$=236-140-94=2$
The other particles are two neutrons. Hence, (a) is not correct. For nuclei, number of protons tells the charge. So, the other particles must have charge $Z$ such that
$92=54+38+Z$
$\therefore Z=0$
Therefore, the other particles have a total atomic mass $2$ and total charge $0$.