Question

Which of the following isotopes of uranium is unstable?
A) U-234
B) U-235
C) U-238
D) All of the above

Answer 1

Uranium is naturally unstable and can be transformed by absorbing or emitting particles. Naturally occurring uranium is composed of three major isotopes.

Complete step by step solution:
$U - 234$, $U - 235$ and $U - 238$ are naturally-occurring three major isotopes of Uranium and all the three isotopes are unstable. And we know that Uranium is naturally unstable.

Uranium can take many chemical forms (including uranium hexafluoride), some of which play an important role in uranium processing. Several possible health effects are associated with human exposure to uranium compounds. Uranium can be processed to make fuel for nuclear reactors.

Let’s discuss all the three major isotopes of uranium, that is, $U - 234$, $U - 235$ and $U - 238$ in detail,
$U - 234$ undergoes alpha decay and changes into $Thorium - 230$ and is considered as an unstable isotope of Uranium.

Now in the case of $U - 235$, it also decays by alpha emission and transforms into $Thorium - 231$ and hence unstable.

$U - 238$ Again undergoes alpha decay and changes into $Thorium - 234$ which transforms into $Protactinium - 234$, then to $Uranium - 234$ and finally to $Lead - 206$. Therefore $U - 238$ is also an unstable isotope.
By analysing the details of the three isotopes of uranium, we understand that all of them are unstable and undergo radiation.

Final answer is: Option (D), All of the above.

Note: It is known that isotopes of an element have the same number of protons and different number of neutrons. Isotopic ratios of natural uranium can be processed for use in the nuclear industry. This results in both depleted uranium (DU) and enriched uranium. Since Uranium is naturally unstable it is used in the manufacture of atomic bombs.