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}`