Which of the following decays does not change the atomic number of the nucleus?

Radioactive decay is the process by which an unstable nucleus transforms to become more stable, often by emitting particles or energy. Whether or not the atomic number changes during a particular decay depends on the nature of the decay process. Let's examine each option one by one: 1. Alpha Decay:
In alpha decay, the nucleus emits an alpha particle, which consists of two protons and two neutrons (essentially a helium nucleus). Since two protons are lost, the atomic number decreases by 2, and the element transforms into another with a different atomic number. This is a change in identity of the element. 2. Beta-minus Decay:
In beta-minus decay, a neutron inside the nucleus converts into a proton, and in the process, it emits an electron (beta-minus particle) and an antineutrino. As a new proton is formed, the atomic number increases by 1, indicating that the nucleus now belongs to a different element. Though the mass number remains unchanged, the identity of the element changes due to the increase in atomic number. 3. Gamma Decay:
Gamma decay is fundamentally different from the other types of decay. In this process, the nucleus does not change its composition of protons or neutrons. Instead, it releases excess energy in the form of gamma radiation, which is high-energy electromagnetic radiation. Gamma emission typically follows alpha or beta decay, when the nucleus is left in an excited state and needs to return to its ground state. Since no protons or neutrons are added or removed, the atomic number remains unchanged, and the element remains the same. The only thing that changes is the energy state of the nucleus. 4. Beta-plus Decay:
In beta-plus decay, a proton is converted into a neutron, and a positron (beta-plus particle) and a neutrino are emitted. As a proton becomes a neutron, the atomic number decreases by 1. Therefore, the element transforms into a new one with a different atomic number, though the mass number stays the same. Among the options, gamma decay is the only process where no change occurs in the atomic number of the nucleus. It involves the emission of electromagnetic energy without any transformation in the number of protons or neutrons. Thus, the identity of the element remains the same, distinguishing it from all other types of decay listed.