ExpertEasy1 markMultiple Choice
AQA GCSE · Question 02.1 · Atomic Structure
Polonium-210 (²¹⁰₈₄Po) is a radioactive isotope that decays by emitting alpha radiation.
Which is the correct decay equation for polonium-210?
Tick (✔) one box.
Polonium-210 (²¹⁰₈₄Po) is a radioactive isotope that decays by emitting alpha radiation.
Which is the correct decay equation for polonium-210?
Tick (✔) one box.
Answer options:
A.
²¹⁰₈₄Po → ²¹⁴₈₆X + ⁴₂He
B.
²¹⁰₈₄Po → ²⁰⁶₈₂X + ⁴₂He
C.
²¹⁰₈₄Po → ²⁰⁶₈₆X + ⁴₂He
How to approach this question
1. Recall what an alpha particle is. It is a helium nucleus, represented as ⁴₂He.
2. Understand what happens during alpha decay: the nucleus emits an alpha particle.
3. Apply the conservation laws:
- The total mass number (top number) must be the same on both sides of the equation.
- The total atomic number (bottom number) must be the same on both sides.
4. Check each option:
- For the new nucleus X, its mass number will be 210 - 4.
- Its atomic number will be 84 - 2.
5. Select the option that matches your calculation.
Full Answer
B.²¹⁰₈₄Po → ²⁰⁶₈₂X + ⁴₂He✓ Correct
The correct equation is ²¹⁰₈₄Po → ²⁰⁶₈₂X + ⁴₂He
Alpha decay involves the emission of an alpha particle (a helium nucleus, ⁴₂He) from an unstable nucleus.
When a nucleus undergoes alpha decay:
- Its mass number (the top number, A) decreases by 4.
- Its atomic number (the bottom number, Z) decreases by 2.
For Polonium-210 (²¹⁰₈₄Po):
- New mass number = 210 - 4 = 206
- New atomic number = 84 - 2 = 82
So, the resulting nucleus is ²⁰⁶₈₂X. The full equation is:
²¹⁰₈₄Po → ²⁰⁶₈₂X + ⁴₂He
Common mistakes
✗ Confusing alpha decay with beta decay.
✗ Adding the mass/atomic numbers instead of subtracting them from the parent nucleus.
✗ Not checking that both mass number and atomic number are conserved.
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