A comprehensive model of chlorine plasma etching of poly silicon in a parallel plate reactor was developed. The Boltzmann transport equation and a bulk plasma model were used to calculate the rate coefficients of electron impact reactions. These coefficients were then used in a transport and reaction model to calculate the atomic chlorine concentration distribution. The same methodology may be applied to other plasma systems as well. Theoretical results for an empty reactor (no polysilicon film) are presented in this paper. Unified plots were developed which relate the electron density, self-sustained electric field, and electron impact coefficients in the bulk plasma to pressure, power, and reactor geometry. The calculated atomic chlorine concentration showed similar dependence on pressure and electrode spacing for either first or second order surface recombination kinetics. Experimental verification of the model predictions is presented in the accompanying paper.