Pattern 2: Bohr Model Radius and Energy Ratios (NEET 2018, 2020, 2022)

Type: Numerical. "Find the ratio of radii/energies for two different orbits or ions." Answer strategy: Radius ∝ $n^{2}$/Z. Energy ∝ $Z^{2}$/$n^{2}$. Always set up a ratio to cancel a_{0} or 13.6 eV. Example PYQ (NEET 2020): Ratio of the radius of 3rd orbit of H to 1st orbit of $He^{+}$: r_{3}(H)/r_{1}($He^{+}$) = (0.529×9/1)/(0.529×1/2) = 9/(0.5) = 18.

Pattern 3: Radioactive Decay Half-Life (NEET 2021, 2024)

Type: Numerical. "What fraction remains after n half-lives?" or "How many half-lives for activity to drop to 1/32?" Answer strategy: Express target fraction as 1/2ⁿ, find n, then time = n × t_{1}/{2}. Example PYQ (NEET 2024): A nucleus has t{1}/_{2} = 3.8 days. Find mass remaining from 15.2 mg after 19 days: n = 19/3.8 = 5 half-lives. Remaining = 15.2/32 = 0.475 mg.

Pattern 4: Nuclear Decay Equation Balancing (NEET 2021, 2024)

Type: Alpha or beta decay product identification. Answer strategy: Alpha: A−4, Z−2. Beta-minus: A same, Z+1. Use conservation of A and Z. Example PYQ (NEET 2021): ^{226}{88}Ra → ? + ^{4}{2}He. A = 222, Z = 86 (Rn). Answer: ^{222}_{86}Rn.

Pattern 5: BE/A Curve Interpretation (NEET 2019, 2022)

Type: Conceptual. "Why does fission/fusion release energy?" Answer strategy: Products have HIGHER BE/A → more stable → energy released = increase in binding energy. Key facts: Fe-56 = 8.75 MeV/n (max); He-4 ≈ 7.07 MeV/n; U-238 ≈ 7.57 MeV/n.

Pattern 6: KE, PE, Total Energy Signs (NEET 2019, 2023)

Type: Trap MCQ. "KE and PE of electron in ground state of hydrogen are respectively:" Answer strategy: $E_{1}$ = −13.6 eV (negative). KE = −$E_{1}$ = +13.6 eV (positive). PE = 2$E_{1}$ = −27.2 eV (negative). Answer: KE = +13.6, PE = −27.2.