Question

${}_{92}^{238}U\stackrel{\alpha }{\to }Y\stackrel{{}_{+}{\beta }^0}{\to }{}_Z^{A}X$, find A & Z.

• A. Z = 87; A = 234
• B. Z = 89; A = 234
• C. Z = 89; A = 236
• D. Z = 87; A = 232

Answer 1

The correct option is B Z = 89; A = 234

First process is an alpha decay.
${}_{92}^{238}U{\to }_q^{p}Y{+}_2^4\alpha$

Hence, $238=p+4$
$92=q+2$
This gives
$p=234$ and $q=90$

In second process, we have a beta + decay
${}_{90}^{234}Y{\to }_Z^{A}X{+}_1^0\beta$

$234=A+0$
$90=Z+1$
Hence $A=234$ and $Z=89$