Question

PLEASE HELP!!
The alpha decay of a radioactive nuclide (X) emits a He-4 nucleus and produces an isotope of 235/92 U, What is X?
A. 235/91 Pa
B. 235/93 Np
C. 236/92 U
D. 239/94 Pu

Answer 1

It's letter D.) 235/92 U + 4/2 He = 239/94 PU

Answer 2

Answer: D) $_{94}^{239}\textrm{Pu}$

Explanation:

Alpha decay : When a larger nuclei decays into smaller nuclei by releasing alpha particle. In this process, the mass number and atomic number is reduced by 4 and 2 units respectively.

General representation of alpha decay :

$_Z^A\textrm{X}\rightarrow _{Z-2}^{A-4}Y+_2^4{He}$

Thus $_{94}^{239}\textrm{Pu}\rightarrow _{94-2}^{239-4}Y+_2^4{He}$

$_{94}^{239}\textrm{Pu}\rightarrow _{92}^{235}U+_2^4{He}$