The reason for chemical properties of noble gas are stable has to be explained.
Noble gases are group 18 elements present in periodic table. The six elements are helium, neon, argon, krypton, xenon and radon. They all have a complete octet structure of complete octet electronic configuration. Hence no electron can be added or removed easily from the shell. Therefore the noble gases are very much stable. Moreover, all other atoms of elements try to attain the octet configuration of noble gases either by losing or gaining of electrons.