Chapter 7 Electron Configurations and the Properties of Atoms 7.1 ...

Chapter 7 Electronic Configurations and the Properties of Atoms
7.1a Electron Spin and the Spin Quantum Number, ms
Although electrons are too small to observe directly, we can detect the magnetic field that they exert.
This magnetic field is generated by electron spin, the negatively charged electron spinning on an axis
(Interactive Figure 7.1.1).
Interactive Figure 7.1.1: Relate electron spin and magnetic properties.
Electron spin and magnetic field
The magnetic field produced by an electron occurs in one of two directions, indicating that electron
spin is quantized. That is, an electron has only two possible spin states. In one spin state, the electron
produces a magnetic field with the North pole in one direction. In the other spin state, the North pole
is in the opposite direction (Figure 7.1.2).
Figure 7.1.2 Electron spin and magnetic fields.
Spin states are defined by a fourth quantum number, the spin quantum number, ms. Because there
are two different spin states, ms has two possible values: +½ or ½. The sign of ms is used to indicate
the fact that the two spin states are in opposite directions and should not be confused with the
negative charge on the electron.
Symbolizing Electron Spin We saw in the previous chapter that lines or boxes can be used to depict
orbitals. Electrons in orbitals are shown using arrows, where the direction of the arrow indicates the
spin state of the electron. For example, in the diagram that follows, the upward () and downward ()
arrows indicate electrons in different spin states.
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