Q1(e). Magic numbers

Answer in brief

Magic numbers correspond to closed proton or neutron shells, separated from the next available levels by relatively large energy gaps.

Key points

• In the nuclear shell model, protons and neutrons occupy quantised single-particle levels in the nuclear potential. Strong spin–orbit splitting helps produce shell closures.
• The familiar magic numbers are 2, 8, 20, 28, 50, 82 and 126.
• Closed shells have extra binding and resist adding or removing a nucleon. Doubly magic examples include ¹⁶O (Z=N=8) and ²⁰⁸Pb (Z=82,N=126).