The title electride crystallizes in the orthorhombic space group Pbcn with a = 10.060(4) Angstrom, b = 23.134(8) Angstrom, c = 8.380(4) Angstrom, and z = 4. A second powdered phase of unknown structure, but with rather different properties, forms when rapidly precipitated "seed" powder is used. The crystalline phase contains electron-trapping cavities, each of approximate diameter 4.3 Angstrom, connected in zigzag fashion along the c axis by rather open channels of minimum diameter 2.4 Angstrom (center-to-center distance 7.9 Angstrom). Each cavity is also connected to next-neighbor cavities, 8.2 Angstrom away along c, by channels of diameter 1.5 Angstrom. Inter-chain channels are <1.0 Angstrom in diameter so that the cavity-channel structure is well-described as "ladder-like". Replacing the trapped electron by Na- in the corresponding sodide, Li+ (cryptand [2.1.1])Na-, results in an orthorhombic structure (space group Pna2(1)). Although the anionic sites in the sodide are only slightly bigger than those in the electride, the channel structure is markedly different, forming a 3-dimensional network. The magnetic susceptibilities of both phases of the electride above 14 K are well-fit by the linear chain Heisenberg antiferromagnetic model with values of J/k(B) of -54 (crystals) and -17.8 K (powder). Both types show marked deviations below 14 K toward greater spin-pairing. This behavior was verified by EPR measurements of intensity vs temperature. The electride was characterized further by two probe pressed pellet conductivity, variable temperature Li-7 MAS-NMR, and DSC.