We have synthesized a new inorganic electride, Sc2C, updating the previously published Sc-C phase diagram. This electride includes the most electronegative cation adjacent to the electride site. We determine that while there needs to be an electropositive cation present in the structure next to the electride site, the upper limit of electronegativity likely falls just above that of aluminum. We find that this material is the first synthesized small band gap semiconductor 2D electride. Along with our exploration of Al2C, the trivalent metal carbides lead to a new design rule for semiconducting 2D electrides: that more electronegative cations in 2D electrides lead to higher hybridization of the electride electron with the metal, resulting in greater splitting of valence and conduction bands. Therefore, based on the electronegativity of the cation, the band gap in these electride materials can be tuned. The small band gap and good conductivity also allow applications as a battery electrode or in IR photodetectors. Semiconducting electrides under photoexcitation could exhibit both interesting reduction and oxidation capabilities, which could be useful for photocatalysis or catalysis. The experimental realization of layered Sc2C will allow predictions of its enormous H2 and F -storage capacities to be explored.