ABSTRACT
Quantum mechanics correctly predicts the properties of the hydrogen atom, a one-electron system. Electrons can interact with each other in two ways. First, the two electrons repel one another electrostatically, which seems like a simple problem to deal with until we remember that we can no longer regard electrons in atoms as localized points. Second, electrons have an intrinsic spin, one consequence of which is that they generate magnetism. The method of electron spin resonance capitalizes on this property by correlating structural properties with the exact microwave energy absorbed by the particle with the unpaired spin, such a particle being called a radical. A very deep principle in physics dictates that two electrons in the same electron cloud must have opposite spins. There are electron clouds other than just the s and p types to which we are restricting ourselves.
