Answer:
The correct answer is "uranium-238".
Explanation:
Uranium-238, is the most abundant isotope of the element uranium. Uranium-238 has not enough nuclear force to balance electrostatic forces between protons, and as a result, it is a radioactive isotope and its losing energy because of the spontaneous breakdown of its atomic nucleus. Uranium-238 has a half-life of 4.5 billion years and is used as fuel in nuclear reactors as well as for dating purposes.
