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Why is uranium-235 useful for fission chain reactions?

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Atomic bomb — atomic bomb The first atomic bomb test, near Alamogordo, New Mexico, July 16, 1945.

Uranium-235 is uniquely useful for nuclear fission chain reactions because it is the only naturally occurring fissile material, meaning its nucleus can be split by slow neutrons.12

It is particularly effective for sustaining a chain reaction for two primary reasons:
* Readiness: It undergoes fission more easily than other isotopes.1
* Neutron Yield: Each fission event releases a significant amount of thermal energy and emits two or more neutrons.1

These released neutrons are critical because they can strike surrounding uranium-235 nuclei, causing them to split and release even more neutrons. This process creates a rapidly multiplying series of fissions. In the context of an atomic bomb, this reaction is designed to be divergent—where the multiplication factor k is greater than one—allowing a massive amount of energy to be generated in a fraction of a second.13