Answer: <u>Sinks towards the outer core
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Explanation: The material which is less dense, means it is lighter in weight. Such substances tend to move more towards the crust of the Earth, whereas the heavier substances like iron, is more towards the core or centre of the Earth. This is because heavier substances tend to sink deeper. That’s why the light elements are found in the crust section of the Earth.
If you talk about the process of fission in the nuclear field then the most used is U-235 because is the easiest to use. Have in mind that the majority of uses of uranium is U-238 but the easiest to be used is U-235
