The often called silver peroxide and silver(II) oxide, AgO or Ag[subscript 2]O[subscript 2], is actually a mixed oxidation state silver(I,III) oxide. A thermochemical cycle, with lattice energies calculated within the "volume-based" thermodynamic approach, explain why the silver(I,III) oxide is more stable than the hypothetical silver(II) oxide. The coordination geometries of silver and copper in their known oxides correlate with those associated to their electron configurations in coordination compounds. The second ionization energy is higher for Ag than for Cu, which can be related to the small size of 3d orbitals and the resulting high electron repulsion for the first transition series elements. (Contains 2 tables, 1 figure and 2 notes.)