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CognitoAtomic structure and radioactivity
Key facts & equations
Structure of the atom
- Protons and neutrons in the nucleus. Electrons orbit in shells.
- Proton: +1 charge, mass 1. Neutron: 0 charge, mass 1. Electron: -1 charge, negligible mass.
- Atomic number (Z) = number of protons. Mass number (A) = protons + neutrons.
- Isotopes: same element, same protons, different neutrons. Same chemical properties.
- Strong nuclear force holds nucleus together (very short range — overcomes electrostatic repulsion).
Types of radioactive decay — fill in the table
| Type | What is it? | Process |
|---|
| Alpha (α) | | |
| Beta minus (β⁻) | | |
| Gamma (γ) | | |
| Beta plus (β⁺) | | |
Properties of the three radiations — fill in the table
| Radiation | Stopped by | Ionising ability | Deflected by fields? |
|---|
| Alpha | | | |
| Beta | | | |
| Gamma | | | |
Nuclear equations
- Alpha decay: mass number −4, atomic number −2. ²²⁶₈₈Ra → ²²²₈₆Rn + ⁴₂He.
- Beta minus decay: mass number unchanged, atomic number +1. ¹⁴₆C → ¹⁴₇N + ⁰₋₁e.
- Gamma emission: no change to mass or atomic number — nucleus just loses energy.
- Check: top numbers (mass) and bottom numbers (atomic) must balance on each side.
Exam questions — 4 questions · 11 marks · AQA 8463 style
⚡ Show all working — the AI marks against the AQA mark scheme. Method marks awarded for correct working even if the final answer is wrong.
1 markAlpha particleAQA 8463 style
What is an alpha particle?
A A high-speed electron
B An electromagnetic wave from the nucleus
C A helium nucleus — 2 protons and 2 neutrons
D A neutron emitted from the nucleus
1 markPenetration comparisonAQA 8463 style
Which type of radiation is most penetrating?
A Alpha
B Beta
C Gamma
D All three are equally penetrating
4 marksNuclear equationAQA 8463 P2 style
Radium-226 undergoes alpha decay to form radon. Write a balanced nuclear equation. Show that atomic number and mass number are conserved. (3 marks)
Hint: Alpha decay: subtract 4 from mass number, subtract 2 from atomic number. Check both numbers balance on each side.
+40 XP
1 markBeta decay atomic numberAQA 8463 style
Carbon-14 undergoes beta minus decay. What happens to the atomic number?
A Decreases by 1
B Increases by 1
C Stays the same
D Decreases by 2
Quick recall flashcards
Module complete! 🎉
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