Question

Which of the following is emitted when ${}_{94}^{239}P$ decays into ${}_{92}^{235}U$?

• A. Gamma Ray
• B. Neutron
• C. Electron
• D. Alpha particle

Answer 1

The correct option is D Alpha particle

The givne reaction : ${}_{94}{Pa}^{239}{\to }_Z^{A}X+{92}^{}{U}^{235}$
Conservation of mass number, $239=A+235$
$⟹A=4$
Conservation of atomic number, $94=Z+92$
$⟹Z=2$
Thus the particle emitted is ${}_2^{4}He$ i.e. alpha particle.