Shell Model
According to the shell model, protons or neutrons tend to form pairs of opposite total angular momentum. Therefore the magnetic moment of a nucleus with even numbers of both protons and neutrons is zero, while that of a nucleus with an odd number of protons and even number of neutrons (or vice versa) will have to be that of the "last", unpaired proton (or neutron). For a nucleus with odd numbers of both protons and neutrons, the total magnetic moment will be some combination of the magnetic moments of both of the "last", unpaired proton and neutron.
Nuclear magnetic moment is only partly predicted by simple versions of the shell model. The magnetic moment is calculated through j, l and s of the "last" nucleon, but nuclei are not in states of well defined l and s. Furthermore, for odd-odd nuclei, one has to consider the two "last" nucleons, as in deuterium. Therefore there are several possible answers for the nuclear magnetic moment, one for each possible combined l and s state, and the real state of the nucleus is a superposition of them. Thus the real (measured) nuclear magnetic moment is somewhere in between the possible answers.
Read more about this topic: Nuclear Magnetic Moment
Famous quotes containing the words shell and/or model:
“If there was one egg in it there were nine,
Torpedo-like, with shell of gritty leather,
All packed in sand to wait the trump together.”
—Robert Frost (1874–1963)
“It has to be acknowledged that in capitalist society, with its herds of hippies, originality has become a sort of fringe benefit, a mere convention, accepted obsolescence, the Beatnik model being turned in for the Hippie model, as though strangely obedient to capitalist laws of marketing.”
—Mary McCarthy (1912–1989)