Magic number

In nuclear physics, magic number is the name given to the numbers of protons or neutrons giving the greatest stability to the nucleus. These numbers are related to the layer structure of the nucleus.

The list of magic numbers is: 8, 20, 28, 40, 50, 82, 126, ...

For example, isotope 208 of lead has 82 protons and 126 neutrons. It is therefore doubly magic and is one of the most stable nuclei.