Playbook
Structure of Atoms and Nuclei
85 q - 1.96/paper - 22% HARD. Radioactive decay at 6%; the Bohr page is scaling laws, and falls to ratios.
- Questions in the bank
- 85
- q/paper (2024–25 papers)
- 1.96
- Tagged HARD
- 22%
- Subtopics
- 3
Strand: Long Tail
When you’ll see it
A Bohr orbit — radius, speed, energy — a spectral line of hydrogen, or a sample decaying with a half-life.
How this chapter is tested
85 q at 1.96 a paper, 22% HARD. Radioactive Decay and Half-Life is the cheap page (18 q, 6%): after n half-lives N = N₀/2ⁿ, and the mean life is 1.44 times the half-life.
The Bohr page (39 q, 28%) is scaling laws: r ∝ n²/Z, v ∝ Z/n, E ∝ −Z²/n². Almost every question is a ratio between two orbits or two atoms, and answering it from the proportion is faster and safer than computing each value.
The hydrogen spectrum (28 q, 25%) is 1/λ = RZ²(1/n₁² − 1/n₂²) with the right lower level: Lyman 1, Balmer 2, Paschen 3. The longest wavelength of a series is its FIRST line, the shortest its limit.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Bohr scaling
r ∝ n²/Z, v ∝ Z/n, E = −13.6Z²/n² eV. Kinetic energy = −E, potential energy = 2E.
Spectral series
1/λ = RZ²(1/n₁² − 1/n₂²). Lyman n₁ = 1 (UV), Balmer 2 (visible), Paschen 3 (IR).
Radioactive decay
N = N₀e^(−λt), T½ = 0.693/λ, mean life τ = 1/λ = 1.44 T½.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Longest vs shortest wavelength in a series
The longest wavelength is the smallest energy jump — the first line (n₂ = n₁ + 1). The shortest is the series limit (n₂ = ∞). Ratio questions print both orders.
Signs of the Bohr energies
Total energy is negative; kinetic energy is its magnitude; potential energy is twice the total. A higher orbit has LESS kinetic energy.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Structure of Atoms and Nuclei notesDrill every structure of atoms and nuclei question
85 questions from the bank, scoped to 3 bundled subtopics.
Drill one subtopic at a time
The 3 subtopics this playbook covers, in catalog order.
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