The metal-metal distances in these M2C systems are all increased with respect to their metallic counterparts, and compared to one another, the Y-Y distance is the largest (3.96 Å), Sc-Sc is in the middle (3.53 Å), and Al-Al is the shortest (3.09 Å). Although one expects a different ionic radius for each cation, the metal-metal distances span such a large range that the differences in metal ionic radii are negligible; we conclude there is an increase in metal-electron hybridization from Y to Sc to Al. From these observations, we propose a model in which increasing electronegativity of metal leads to increased hybridization between unoccupied metal orbitals and the electride electron. This hybridization is because of similar energies and because of spatial proximity. Increased hybridization between electride state and empty orbitals leads to greater splitting between the filled valence band and empty conduction band -and thus a larger band gap. The relatively large amount of hybridization in the Al2C structure would lead to a small amount of electron localization. Al2C as a low electride character species supports the idea that neighboring cation electronegativity plays a role in materials exhibiting electride character, and the limit of cation electronegativity in electride materials likely lies somewhere just below the electronegativity value of aluminum.