Which element is the end product of each natural radioactive series?

Consider an $\alpha$-particle just in contact with a $_{92}U^{238}$ nucleus. Calculate the coulombic repulsion energy (i.e.,the height of the coulombic barrier between $U^{238}$ and $\alpha$-particle) assuming that the distance between them is equal to the sum of their radii.

The fuel used in an atomic pile is

An atomic nucleus having a low $n/p$ ratio tries to find stability by:

Emission is caused by the transformation of one neutron into a proton. This results in the formation of a new element having

Which among the following minerals contains a radioactive element?