Which type of radioactive decay results in an increase in the atomic number of the parent nucleus by one, while keeping the mass number unchanged?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. Beta-minus decay.
In beta-minus (β-) decay, a neutron inside the parent nucleus is converted into a proton, an electron (beta particle), and an antineutrino. Since a neutron is replaced by a proton, the atomic number (Z) increases by one (e.g., from 6 to 7), while the mass number (A) remains unchanged because the total number of nucleons stays the same. This process typically occurs in nuclei that have an excess of neutrons, moving them toward a more stable state.
Other Options:
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Alpha decay: Emits a helium nucleus, decreasing the atomic number by 2 and the mass number by 4.
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Beta-plus decay: A proton converts to a neutron, decreasing the atomic number by 1 while the mass number stays constant.
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Gamma decay: Emits high-energy photons; it changes neither the atomic number nor the mass number, only the energy state.