Question

In the decay sequence, ${}_{92}^{238}U\stackrel{-x_1}{\to }{}_{90}^{234}Th\stackrel{-x_2}{\to }{}_{91}^{234}Pa\stackrel{-x_3}{\to }{}^{234}Z\stackrel{-x_4}{\to }{}_{90}^{230}Th{x}_1,x_2,x_{3}and{x}_4$ are particles /radiation emitted by the respective isotopes. The correct option(s) is/are:

• A. $x_3$ is $\gamma -ray$
• B. Z is an isotope of uranium
• C. $x_2$ is ${\beta }^{-}$ decay
• D. $x_1$ will deflect towards negatively charged plate

Answer 1

Answer: (B), (C), (D)

$x_1$ will deflect towards negatively charged plate

a) Given ${}_{91}^{234}Pa\stackrel{-x_3}{\to }{}^{234}Z$
Since the mass number does not change, $x_3$ is ${}_{-1}^{0}e$ i.e. ${\beta }^{-}$. So $x_3$ is not $\gamma$-ray.
b) Isotopes are elements which have the same atomic number but different mass number. Thus Z is an isotope of uranium.
c) ${}_{90}^{234}Th\to {}_{91}^{234}Pa{+}_{-1}^{o}e$. Thus $x_2$ is ${\beta }^{-}$.
d) ${}_{92}^{238}U\to {}_{90}^{234}Th{+}_2^{4}H{e}^{2+}$. So $x_1$ is an $\alpha$-particle and hence will get deflected towards the negatively charged plate.