What are certain numbers of nucleons, known as magic numbers stable against?
half-lifes
water
radiation
nuclear decay
certain numbers of nucleons, known as magic numbers, are stable against nuclear decay. These numbers of protons or neutrons (2, 8, 20, 28, 50, 82, and 126) make complete shells in the nucleus. These are similar in concept to the stable electron shells observed for the noble gases. Nuclei that have magic numbers of both protons and neutrons, such as 42 He, 168 O, 40 and 208 are called “double magic” and are particularly stable. These trends in 20 Ca, 82 Pb, nuclear stability may be rationalized by considering a quantum mechanical model of nuclear energy states analogous to that used to describe electronic states earlier in this textbook. The details of this model are beyond the scope of this chapter. Stable Nuclear Isotopes Number of Stable Isotopes.