When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom.

Options

A. do not change for any type of radioactivity
B. change for `alpha` and `beta-` radioactivity but not for `gamma-` radioactivity
C. change for `alpha-` radioactivity but not for other
D. change for `beta-`radioactivity but not for other

Explanation

To solve the question regarding the changes in electronic energy levels of an atom when its nucleus undergoes radioactive decay, we will analyze the three types of radioactive decay: alpha decay, beta decay, and gamma decay.

### Step-by-Step Solution:

1. **Understanding Electronic Energy Levels**:
- The electronic energy levels of an atom depend on its atomic number (Z), which is the number of protons in the nucleus. In a neutral atom, the number of electrons is equal to the number of protons.

2. **Analyzing Alpha Decay**:
- In alpha decay, the nucleus emits an alpha particle, which consists of 2 protons and 2 neutrons.
- This results in a decrease in the atomic number (Z) by 2 (Z' = Z - 2).
- Since the atomic number changes, the electronic energy levels will also change.

3. **Analyzing Beta Decay**:
- In beta decay, a neutron in the nucleus is transformed into a proton, emitting a beta particle (an electron).
- This process increases the atomic number (Z) by 1 (Z' = Z + 1).
- Again, since the atomic number changes, the electronic energy levels will change.

4. **Analyzing Gamma Decay**:
- Gamma decay involves the emission of gamma radiation, which is a high-energy photon.
- In this process, there is no change in the number of protons or neutrons; thus, the atomic number remains the same (Z' = Z).
- Since there is no change in atomic number, the electronic energy levels do not change.

5. **Conclusion**:
- From the analysis, we can conclude that the electronic energy levels of the atom change during alpha and beta decay but remain unchanged during gamma decay.

### Final Answer:
The correct option is: **Change for alpha and beta decay but not for gamma radioactivity.**

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