I am trying to get to the bottom of a few things in the Stern-Gerlach experiment. First, on wikipedia, it says

The Sommerfeld model predicted that the magnetic moment of an atom measured along an axis will only take on discrete values.

The wikipedia page also says that Stern-Gerlach was meant to test the Bohr-Sommerfield hypothesis that the direction of angular momentum is quantized.

So, what I am wondering is exactly how the choice of silver atoms achieves this? I know that the chemistry of the silver atoms is such that the net angular momentum for the first 46 electrons is zero, and the small magnetic moment of the nucleus allows us to focus on the electron. My questions are:

  1. How did they know, at the time of the experiment, that the first 46 electrons had no angular momentum at all?
  2. How do we isolate intrinsic and extrinsic momentum in this experiment for the 47th electron? I assume at this time, there was not such a distinction, but knowing that there is now, how to we isolate spin as something independent? Did they just interpret that, indeed, the direction of angular momentum is quantized, and only later the concept of spin was developed to isolate this factor that is quantized?


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