Atomic and nuclear physics (internal)
Internal 3 credits Atomic models Energy levels Photons Spectra Radioactivity Nuclear equationsAS 91172, 3 credits. Atomic MODELS (Thomson, Rutherford, the gold foil experiment — a required topic often skipped), energy levels, photons and spectra, radioactive decay and nuclear reactions. The ladder: Achieved shows awareness of how simple facets relate to a described situation, Merit gives REASONS why — and for calculations, Merit means the information is not directly usable or immediately obvious.
1 Reading the notation
Atomic models and the gold foil experiment are their own named topic — often the one skipped entirely.📖 Terms the schedule grades you on
4 terms- Demonstrate understanding (Achieved)
- Awareness of simple facets relating to a described situation.
- In-depth (Merit)
- Reasons WHY; calculations where info is NOT directly usable/immediately obvious.
- Comprehensive (Excellence)
- Connections BETWEEN concepts.
- Assessment scope (note 4)
- Atomic models (Thomson/Rutherford, gold foil); nuclear transformations; conservation of A and Z; power/E=mc²/P=E/t/emission properties.
2 Atomic models and the gold foil experiment
A named, required topic — plum pudding, replaced by the nuclear model, and why.| Observation | What it implies about atomic structure |
|---|---|
| Most alpha particles pass straight through | The atom is mostly empty space |
| Some deflect at small angles | There is a concentration of charge somewhere |
| A few bounce almost straight back | That charge is concentrated in a tiny, dense, positive nucleus |
This experiment is its own named assessment topic (note 4) — skipping it entirely misses a quarter of the standard's scope.
3 Energy levels, photons and spectra
Discrete levels produce discrete lines — the whole point of the model. ✕Treating emission and absorption lines as unrelated
Emission and absorption spectra for the same element show lines at the SAME wavelengths, because the same energy-level gaps are involved either way — this is how elements are identified in starlight, and it is worth stating explicitly rather than treating the two spectrum types as separate phenomena.4 Radiation, decay, and conservation
Balancing A and Z on both sides IS the "conservation of atomic and mass number" named in note 4.The three radiations at a glance
- Alpha: helium nucleus, stopped by paper, strongly ionising.
- Beta: electron, stopped by a few mm of aluminium.
- Gamma: EM wave, reduced (not stopped) by thick lead, weakly ionising.
5 The calculations that decide the grade
Merit means the information is not directly usable — an extra step is required.What to have memorised
Photon energy E = hf = hc/λ h = 6.63 × 10⁻³⁴ J s Wave relationship c = fλ c = 3.00 × 10⁸ m s⁻¹ Remaining fraction N = N₀ × (1/2)ⁿ n = number of half-lives elapsed Mass–energy E = mc² The mass defect becomes the released energy Power P = E/t Often combined with E = mc² for a two-step Merit question Internal-style A sample falls to 12.5% of its original activity in 24 days Find the half-life. 12.5% = 0.125 = 1/8. 1/8 = (1/2)³, so n = 3 half-lives have elapsed. Half-life = 24 ÷ 3 = 8 days. ✓ 8 days. The number of half-lives was not given — deriving it from the fraction is exactly the "not immediately obvious" step that makes this Merit rather than Achieved.Practice
Recall it first, then use it — testing yourself builds the memory, where rereading the notes above only feels easier.
Recall and application shuffled together — you have to work out what each item wants before you can answer it, which is the part the exam actually tests. Both kinds feed the same spacing schedule, so anything you miss comes back sooner.
Say the answer out loud before flipping — that attempt is where the learning happens, even when you get it wrong.
Exam-style only. Instant feedback, shuffled each attempt, best score saved on this device.