Zirconium La radiation has been utilized to investigate the chemical bonding in silicon compounds by x-ray photoelectron spectroscopy. The compounds studied in the present investigation are SiO2, SiO, SiC, Si3N4, and silicon-oxynitrides. The spectra in the Si Is and KLL Auger regions were recorded for these compounds and compared with the elemental spectra. In order to estimate the change in chemical environment of Si in these compounds, the Auger parameter was determined in each case as the difference between the binding energies for the Is and the KLL peaks. The trend in the value of the Auger parameter is correlated with the degree of atomic relaxation due to the increasing neutralization of charge around the Si cations in these compounds. A good agreement was found between the change in the Auger parameter and the bond ionicity calculated for the Si cation in these compounds. Using this plot, the bond ionicities were determined for the oxynitrides. A model is also developed to estimate these ionicities from the concentrations of oxygen and nitrogen present in these compounds. The values of the ionicities obtained by these two different methods give a satisfactory agreement. We have shown that the plot between the change in the Auger parameter and the bond ionicity could be used to estimate the bond ionicities.