Why do atomic nuclei with odd number of protons behave as magnets when introduced to a magnetic field?
In: Physics
It does not have to do with the number of protons. It has to do with the electron spin configurations.
Protons have a magnetic moment/spin just like electrons do, if you have an even number then they pair up with each in the pair having opposite spins so they cancel out, if you have an odd number then there will always be one left without a partner
The magnetism of an atom comes from its electrons. Each electron shell can hold a pair of electrons – one with “up” spin and one with “down” spin. Electron spin isn’t the same as normal spinning, but it’s also not *not* like normal spinning. The spin of the electron creates a tiny magnetic field.
When the shell has both electrons, their spins cancel each other out so there is no overall magnetic field. When there isn’t a pair, there is one electron more with that direction of spin than the other direction, so its magnetic field isn’t opposed by another electron. This gives the atom an overall net magnetic field.
Atoms *generally* have the same number of electrons as they have protons. An imbalance between the two creates a charged ion, which is very likely to either capture an electron or eject an electron so that the charge becomes neutral again. So an odd number of protons means an odd number of electrons, which means the outer shell doesn’t have a balanced spin, so it has a tiny magnetic field associated with that spin.
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