Nuclear Physics

Step 1: Understanding the Concept:
decay: mass number decreases by 4, atomic number by 2. decay: mass number unchanged, atomic number increases by 1.

Step 2: Detailed Explanation:
Start:
After 3 decays: Mass = 228 - 3×4 = 216, Atomic = 88 - 3×2 = 82.
After 1 decay: Mass = 216 (unchanged), Atomic = 82 + 1 = 83.
Element with Z=83 is Bi. So Y = .

Step 3: Final Answer:

Concept: Nuclear reactions must conserve mass number and atomic number.

Step 1: Check conservation.
In option (B), both mass and atomic numbers balance correctly.

Step 2: Other options.
They violate conservation laws.

Step 3: Conclusion.
Correct answer is (B)

Concept: Positron emission ( decay) is a type of radioactive decay in which a proton inside the nucleus is converted into a neutron, a positron ( ), and a neutrino ( ):

Step 1: Effect on proton and neutron numbers.
• Number of protons ( ) decreases by 1
• Number of neutrons ( ) increases by 1
• Mass number ( ) remains constant

Step 2: Effect on ratio. Initial ratio = . After decay: The ratio increases because the number of neutrons increases while the number of protons decreases.

Step 3: Conclusion. During positron decay, the ratio increases.