The study of the character of collective electron density oscillations provides a fundamental understanding of the optoelectronic and photonic behavior of nanostructures. Consequently, electron-energy loss spectroscopy represents an important method for the structure analysis of materials with metallic nanoparticles since it contains valuable information about size, geometry and chemical composition of the particles and in addition, their spatial configuration, distance and crystalline order. Therefore, analytical model calculations and a parameter study were accomplished based on the hydrodynamic and density functional theory. Eigenfrequencies of plasmons were calculated and theoretical energy loss spectra were obtained by modelling the associated energy loss functions. Electron-energy losses appear at energies below 5 eV, far below the well-known dipole resonance energy of metallic spheres. The energy positions are dependent on the electron density, geometry, particle size, distance and crystalline structure of the particle arrangement.