Equation ( ) shows how the chemical potential of an atom A, in a molecular environment, is a function of its electronegativity. Note that the label A marks the specific atom for which the chemical potential µ L is evaluated, while the index α runs over all atoms in the molecule. At face value, eq. ( ) looks similar to eq. ( ). However, the latter describes the properties of the whole system, with no external forces influencing its chemical potential. In contrast, eq. ( ) makes explicit the connection between the electronegativity and the chemical potential of an atom within a molecular environment. Expressing chemical potentials of atoms as in eq. ( ) provides a perspective closely related to the well-known example of a junction between p-and n-type semiconductors. When two different semiconductors are put in contact, electrons flow from a higher chemical potential to a lower one. In a p-n junction, the chemical potential is homogeneous at equilibrium. However, each side of the junction is still expressed as a sum of two inhomogeneous quantities. One is a local potential, which relates to the type of the semiconductor. The second is an external electrostatic potential, which arises from inhomogeneous doping of the two semiconductors. We argue that the flow of electrons between bonded atoms can be described in similar terms, by the chemical potentials provided by eq. ( ).