Part 1: Key Ideas and Worked Examples

Conservation rules: In a nuclear equation, the total nucleon number (mass number, A) and the total proton number (atomic number, Z) must be conserved. The totals on the left and right sides must be equal.

Notation: A nuclide is written as ^A_Z X, where A is the nucleon number and Z is the proton number.

Reference table:

Alpha (α): ^4_2 α is emitted. The daughter nucleus has A reduced by 4 and Z reduced by 2.

Beta-minus (β⁻): ^0_-1 β⁻ is emitted. A is unchanged and Z increases by 1.

Gamma (γ): ^0_0 γ is emitted. A and Z are unchanged; the nucleus loses energy.

Worked examples

Alpha decay: ^238_92 U → ^234_90 Th + ^4_2 α

The emitted alpha particle removes 4 nucleons and 2 protons, so both A and Z decrease by these amounts.

Beta-minus decay: ^14_6 C → ^14_7 N + ^0_-1 β⁻

The nucleon number stays the same, while the proton number increases by 1.

Gamma decay: ^99m_43 Tc → ^99_43 Tc + ^0_0 γ

Gamma emission releases energy only, so the nucleon number and proton number do not change.

Part 2: Graduated Practice

Part 3: Answer Key

1. Alpha decay.

2. Beta-minus decay.

3. Gamma decay.

4. ^206_82 Pb

5. ^90_39 Y

6. ^0_-1 β⁻

7. ^238_92 U

8. ^131_53 I

9. ^24_11 Na

10. Alpha decay; ^4_2 α

11. Beta-minus decay; ^3_2 He

12. Gamma decay; ^152_63 Eu