Step-by-step explanation:
The fission process:
Initially, the reaction starts with the fission of an atom with an unstable nucleus. In fission, neutrons are produced, and they travel through the surrounding medium. Eventually, they meet other atoms and they are captured by their nuclei: the nuclei become unstable and they undergo fission as well.
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Order of the events according to the explanation: answer
1) One uranium atom fission.
2) Neutrons are produced from the uranium atom.
3) Neutrons find other uranium atoms.
4) Many uranium atoms fission.