A single electron floating in empty space has a known g-factor of exactly 2.0023. However, an electron trapped inside a real molecule behaves in a very different way. The electron moves through complex orbital paths around the heavy atomic nuclei.
This rapid movement creates a small magnetic pull known as spin-orbit coupling. This extra magnetic pull shifts the electron’s g-factor away from the standard value. The exact shift depends on the shape and chemical makeup of the whole molecule.
Chemists can measure this shifted value using a powerful machine called an EPR spectrometer. The final reading tells them exactly where the unpaired electrons live inside the structure. This technique is incredibly useful for studying unstable radicals and large transition metals.
Students often assume that the g-factor is always a single fixed number. In reality, a molecule has different values depending on how it faces the magnet. Chemists call this effect a g-tensor, which gives three separate numbers for different directions.
The famous equation connecting all these scientific ideas is written as hν = gμBB. This math matches the applied microwave energy to the exact magnetic field strength.