²³⁵U is readily made fissionable by a thermal neutron but ²³⁸U is not because: A)the neutron has a smaller binding energy in ²³⁶U B)the neutron has a smaller excitation energy in ²³⁶U C)the potential barrier for the fragments is less in ²³⁹U D)the neutron binding energy is greater than the barrier height for²³⁶U and less than the barrier height for ²³⁹U E)the neutron binding energy is less than the barrier height for ²³⁶U and greater than the barrier height for ²³⁹U

Question

Quizplus · Accepted Answer

For a nucleus to undergo fission, the neutron binding energy should be greater than the barrier height. In ²³⁶U, the neutron binding energy is greater than the barrier height, making it fissionable by a thermal neutron. In ²³⁹U, the barrier height is less than the neutron binding energy, making it not fissionable by a thermal neutron. Therefore, choice D is the correct answer.

235U Is Readily Made Fissionable by a Thermal Neutron but 238U

²³⁵U Is Readily Made Fissionable by a Thermal Neutron but ²³⁸U