Germanenes electronic and optical properties have been determined from ab initio' calculations, and structural and electronic properties from first principles. These properties make the material suitable for use in the channel of a high-performance field-effect transistor and have generated discussion regarding the use of elemental monolayers in other electronic devices. The electronic properties of germanene are unusual, and provide a rare opportunity to test the properties of Dirac fermions. Germanene has no band gap, but attaching a hydrogen atom to each germanium atom creates one. These unusual properties are generally shared by graphene, silicene, germanene, stanene, and plumbene.