It describes the angular momentum of the electron.

它描述的是，电子的叫角动量。

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And the first is l, and l is angular momentum quantum number, and it's called that because it dictates the angular momentum that our electron has in our atom.

第一个就是l，l是,角动量量子数，叫它这个名字,是因为它表明，原子中,电子的角动量是多少。

麻省理工公开课 - 化学原理课程节选