Binding energy per nucleon vs mass numberप्रति न्यूक्लिऑन बंधन ऊर्जा बनाम द्रव्यमान संख्याBinding energy per nucleon vs mass number

NCERT Fig 13.1 · Class 12 Physics · Chapter 13 · interactive diagram

Parts and what they mean

• The curve (real data) (वक्र (वास्तविक आँकड़े)) — Each dot is one nucleus; its binding energy per nucleon E_bn = E_b/A is worked out from its measured atomic mass. Higher on the curve = more tightly bound.
• ²H (deuteron): 1.11 MeV (²H (ड्यूट्रॉन): 1.11 MeV) — Very loosely bound — only 2.22 MeV holds the proton and neutron together.
• ⁴He: 7.07 MeV (⁴He: 7.07 MeV) — A sharp peak among light nuclei — ⁴He is unusually stable (evidence of shell structure).
• ¹²C: 7.68 MeV (¹²C: 7.68 MeV) — Another bump: ¹²C (and ¹⁶O) are more tightly bound than their neighbours.
• ¹⁶O: 7.98 MeV (¹⁶O: 7.98 MeV) — E_b = 127.6 MeV for 16 nucleons (NCERT Example 13.3 gets 127.5 MeV).
• ⁵⁶Fe: 8.79 MeV — the peak (⁵⁶Fe: 8.79 MeV — शिखर) — Maximum of the curve near A = 56 (NCERT: about 8.75 MeV). Iron-group nuclei are the most tightly bound.
• ¹²⁰Sn: 8.50 MeV (¹²⁰Sn: 8.50 MeV) — A typical A ≈ 120 fission fragment: about 8.5 MeV per nucleon (used in the 200 MeV estimate).
• ²³⁸U: 7.57 MeV (²³⁸U: 7.57 MeV) — Heavy nuclei are less tightly bound (NCERT: 7.6 MeV for A = 238). Proton–proton repulsion grows with Z.
• Flat middle region (समतल मध्य भाग) — For 30 < A < 170, E_bn is nearly constant (~8 MeV) — because the nuclear force is short-ranged and saturates.
• Fusion side (light nuclei) (संलयन पक्ष (हल्के नाभिक)) — Joining two very light nuclei gives a nucleus higher up the curve → energy is released (the Sun).
• Fission side (heavy nuclei) (विखंडन पक्ष (भारी नाभिक)) — Splitting a heavy nucleus into two middle-mass nuclei moves up the curve → energy is released (reactors).

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 13.1. Report a mistake