Why does Noble gas not react and Xenon reacts?

Xenon is also having 8 electrons in its outermost shell but because of its large size the outermost orbital is loosely attracted to the nucleus. So they become available for reaction. read more

First, you forgot that Xenon is also noble gas. Noble gases react under special circumstances, except that helium does not, according to all observations and experiments to date. Xenon is especially active among noble gases due to its large radius, which means less restrain from the nucleus on the electrons on the outermost level. read more

Noble does not mean unreactive, it means it shows little reactivity. All the noble gases can be protonated and most react with very electronegative species (O, F). read more

Many other compounds of xenon and then krypton followed. Some are explosively unstable: Bartlett nearly lost an eye studying xenon dioxide. Radon, a heavier, radioactive noble gas, forms compounds too, but it wasn’t until 2000 that the first argon compound, argon fluorohydride, was reported to exist at low temperatures by a group at the University of Helsinki, Finland (Nature, vol 406, p 874). Even now, the noble gases continue to produce surprises. read more

Noble gases are considered to be chemically inert, because they typically do not react with other materials. In ordinary conditions, the are perfectly inert. This does not mean that they cannot react with other materials. Scientists can make them react in laboratories, under special conditions. read more