Paired electrons are two electrons that occupy the same orbital with opposite spins. The opposite spins are required by the Pauli exclusion principle, which limits any orbital to two electrons. Their magnetic effects cancel, so fully paired species are diamagnetic, in contrast to species with unpaired electrons.

成对电子是占据同一轨道、自旋相反的两个电子。自旋相反是泡利不相容原理的要求,该原理将任一轨道限制为最多两个电子。它们的磁效应相互抵消,故完全成对的物种呈抗磁性;与之相对的是含未成对电子的物种。