9.1 Introduction9.2 Bloch Theorem and Bloch Functions9.3 Kronig–Penney Model of Behavior of an Electron in a Periodic Potential9.4 New Interpretation of Momentum, Velocity, and Mass of Electrons Derived from the Kronig–Penney Model of Motion of Electrons in a 1D Periodic Crystal9.5 E–K Relationships in Various Representations9.5.1 Periodic Zone Scheme9.5.2 Extended Zone Scheme9.6 Number of Possible States or Wavefunctions in an Energy Band9.7 Energy Band Calculations9.7.1 Origin of the Energy Gap9.7.2 The NFE Approximation9.7.3 The TB Approximation9.7.4 Energy Bands in Insulators, Semiconductors, and Metals9.8 Fermi Surfaces9.8.1 The Harrison Method of Constructing the Fermi Surfaces9.8.2 Fermi Surfaces in Metals9.9 The Experimental Study of Fermi Surfaces9.9.1 The dHvA Effect9.9.2 Cyclotron ResonanceSummaryProblemsReferences