To understand how cation electronegativity plays a role in band structure, we compare these results to the electronic structure of Y2C and Al2C. The known hybrid electride Y2C has a similar ELF to Sc2C, where there is electron character that is not associated with either the yttrium or carbon atoms (Figure ). Yttrium has an electronegativity value of 1.22, whereas scandium has a value of 1.36 . Therefore, Sc2C is the 2D electride with the most electronegative metal adjacent to the electride site yet synthesized. We wanted to further explore a possible electride structure with a similar, yet more electronegative metal, aluminum (1.61). A layered Al2C has a similar structure to that of both Y2C and Sc2C with a space group of R3 � m, and there is observed electron localization in this structure between the layers of Al2C (Figure ). We calculated band structures and band gap of Y2C (Figure ), Sc2C, and Al2C (Figure ) using the same calculation parameters. Y2C is a semimetal, while Sc2C and Al2C are indirect band gap semiconductors, where the band gap increases from 0.31 to 0.50 eV as the electronegativity of the cation increases.