Atoms Have Angular Momentum and Magnetism
shows a negatively charged particle moving in a circular orbit around a fixed center. As we discussed in Section 32-4, the orbiting particle has both an angular momentum ‘[ and (since its path is equivalent to a tiny current loop) dipole moment ji. (Here, for brevity, we drop the subscript orb that we u ed in Chapter 32.) As shows, vectors ‘[ and ji. are both perpendicular to the plane of the orbit but, because the charge is negative, they point in opposite directions. The model of is strictly classical and does not accurately represent an electron in an atom. In quantum physics, the rigid orbit model has been replaced by the probability density model, best visualized as a dot plot. In quantum physics, however, it is still true that in general, each quantum state of an electron in an atominvolves an angular momentum ‘[ and a magnetic dipole moment ji. that have opposite directions (those vector quantities are said to be coupled).