The Concept of Quantum Numbers-a
Simplified Approach
The concept of quantum numbers is often difficultwhen introduced for the first time. Since this topic is often discussed in interdisciplinary courses, and to nanscience students, it is sometimes helpful to use an analogy to help explain the idea. Two such analogies are pmented here. The four quantum numbers may he treated as an "address" by which one locates a. particular electron in an atom. The principal quantum number, n,is analogous to a state of the union in the address label; the azimuthal quantum number, 1, the city; the magnetic quctntnm number, mz, the street address; and the spin quantum number, m., the "apartment" in which the electron is finally located. In the secand approach, the electron becomes andogous to a. bird on a tree branch. (This approach is, perhaps a less serious one, but is meaningful to botanists and nature lovers!) A man, the nucleus, owns a number of trees. The birds sit on the trees. Each tree is fmther from the owner. (The location of each tree is specified by the principal quantum number. n = 1is the tree closest to the owner.) The number of branches on the tree is determined by how far the tree is from the owner. 1 = 0 1 . . n - 1 ) The fine branching (mr) is governed by the value of 1. Finally, on each mz small branch, two birds can perch, a red one (m. = +1/2) and a blue one fm. . .= -1/2). . . Kring this approach, one ran easily exrend thedisrussion to dectrorr rapariry of each quarturn level (nunher of Lids in, ~ a c htree), urhlrnl diagrams, and elevtron ronligwatiorts. We have fuuud this appnmrh to he n rarher palnles; u.sy of iutrudurulp, an abstract vonwpr that is often troublesome to students
Volume 48, Number
7,July 1971 / 485
