During radioactive decay:

Options

A. atomic mass number cannot increases
B. atomic number may increase
C. atomic number may decrease
D. atomic number may remain unchanged

Answer

**Step-by-Step Solution:**

1. **Understanding Radioactive Decay:**
Radioactive decay is a process by which unstable atomic nuclei lose energy by emitting radiation. This can result in a change in the atomic mass number and atomic number of the nucleus.

2. **Types of Decay:**
There are several types of radioactive decay, including:
- Alpha decay
- Beta minus decay (β-)
- Beta plus decay (β+)
- Gamma decay (γ)

3. **Effect on Atomic Mass Number:**
- In **alpha decay**, the atomic mass number decreases by 4 (because an alpha particle, which consists of 2 protons and 2 neutrons, is emitted).
- In **beta minus decay**, the atomic mass number remains unchanged, but the atomic number increases by 1 (a neutron is converted into a proton).
- In **beta plus decay**, the atomic mass number remains unchanged, but the atomic number decreases by 1 (a proton is converted into a neutron).
- In **gamma decay**, there is no change in either the atomic mass number or atomic number; it only involves the release of energy.

4. **Analyzing the Options:**
- **Option A:** "Atomic mass number cannot increase." This is correct because, in all types of decay, the mass number does not increase.
- **Option B:** "Atomic number may increase." This is correct due to beta minus decay.
- **Option C:** "Atomic number may decrease." This is correct due to alpha decay and beta plus decay.
- **Option D:** "Atomic number may remain unchanged." This is correct for gamma decay.

5. **Conclusion:**
All options A, B, C, and D are correct regarding the possibilities of changes in atomic mass number and atomic number during radioactive decay.

**Final Answer:** All options A, B, C, and D are correct.

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