1) Nuclear reaction.
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2) Types of radioactive decay.
2.1- Alpha decay: the nuclei emit an alpha particle. The mass number decreases by 4, and the atomic number increases by 2.
2.2- Beta-decay: the nuclei emit a fast-moving electron. The mass number does not change, and the atomic number increases by 1.
2.3- Gamma decay: the nuclei emit excess energy. The mass number and the atomic number do not change.
According to the information above the nuclear equation corresponds to an alpha decay.