Abstract: With the theory of statistical physics dealing with chemical reaction (the law of mass action),we analyzedifferent thermodynamic property of noble gases (mono-atomic gases) in a small bubble and diatomic gases in a smallbubble semi-quantitatively.As bubbles of the mono-atomic and the diatomic gases are compressed,shock waves areproduced in both bubbles.Though shock wave leads to sharp increase of pressure and temperature of gases in the bubble,diatomic gas will excitated vibrations and dissociate themselves to mono-atomic gas?these processes will consume manyaccumulated heat energy and block the further increase of the temperature.Therefore,compare with the mono-atomicgases in the bubble,there will be no enough charged particles ionized to flash for diatomic gases in the bubble,this maybe the reason why a bubble of diatomic gases has no single bubble sonoluminescence while a bubble of noble gases has.