A certain material has a molar mass of M = 21.8 g/mol, a Fermi energy of EF = 5.16 eV, and 2 valence electrons per atom. What is its density? Number Units V\f(a) What is the maximum wavelength of the light that will excite an electron in the valence band to the conduction band of an insulator with an energy gap of 6.94 eV? (b) In what part of the electromagnetic spectrum does this wavelength lie? (a) Number HJ Unit v B