Proton or neutron counts such as 2, 8, 20, 28, 50, 82 and 126 that give especially stable nuclei.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
Magic numbers are proton or neutron counts of 2, 8, 20, 28, 50, 82 and 126 that give especially stable nuclei. They are analogous to the noble gas configurations of electrons, because nuclear shells are filled at these numbers. Nuclei that are doubly magic, with magic numbers of both protons and neutrons, are particularly stable, as in helium-4, oxygen-16 and lead-208. Magic numbers explain many observed properties, such as the abundance of stable nuclides. The nuclear shell model accounts for them.
Key ideas: Nuclei with 2, 8, 20, 28, 50, 82 or 126 protons or neutrons are especially stable, like closed electron shells. Doubly magic nuclei include 4He (2,2), 16O (8,8), 40Ca (20,20), 48Ca, 208Pb (82,126). They have higher binding energy, more isotopes and isotones, and lower neutron capture cross sections. The nuclear shell model explains them with spin-orbit coupling.
Common mistakes and connections: Students confuse magic numbers with the 2, 8, 18, 32 electron shell sizes; they are different. Another error is thinking that magic nuclei cannot be radioactive; they are just more stable. Magic numbers guide predictions of long-lived superheavy nuclei, linking to the island of stability.
Nuclei with 2, 8, 20, 28, 50, 82 or 126 protons or neutrons are unusually stable, like filled electron shells; Pb-208 is doubly magic. The interactive lesson shows this as a live animation or chart.
Lead-208 has 82 protons and 126 neutrons, both magic numbers, which makes it exceptionally stable.
Proton or neutron counts such as 2, 8, 20, 28, 50, 82 and 126 that give especially stable nuclei.
Magic Numbers is a advanced topic in Atomic Structure & Periodicity. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Atomic Structure & Periodicity first: Nuclear Fission, Nuclear Fusion, Radiocarbon Dating.
The next topics in Atomic Structure & Periodicity are Island of Stability and Zeeman Effect.
Yes. The interactive lesson includes a self-check question on Magic Numbers, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Magic Numbers is topic 111 of 115 in Atomic Structure & Periodicity.