In eq. ( ), n L is the electronic population of an atom A, and the subscript {n [ } [dL means that G is differentiated at constant populations for all atoms except A. Note that this atomic chemical potential has the same functional form as the macroscopic chemical potential of a component in a multi-component mixture. However, here n L is the number of electrons attributed to atom A, while in a macroscopic system n L would represent the number of particles of component A in a mixture. Following the same reasoning illustrated before for an ensemble of n-electron molecular systems (see eq. ( )), we can express the atomic chemical potential as: