Higher Tier Only: Nuclear Equations in Detail

At higher tier, you must be able to complete and balance nuclear equations. The rules are:

• The sum of mass numbers on the left = sum of mass numbers on the right
• The sum of atomic numbers on the left = sum of atomic numbers on the right

Example — Alpha decay of radon-220:

²²⁰₈₆Rn → ?_?X + ⁴₂α

Mass number: 220 = ? + 4 → ? = 216

Atomic number: 86 = ? + 2 → ? = 84 → element is Polonium (Po)

Answer: ²²⁰₈₆Rn → ²¹⁶₈₄Po + ⁴₂α

Beta decay example: In ⁰₋₁β, the "−1" atomic number counts in the balance.