The periodic table
Noble gas — নিষ্ক্রিয় গ্যাস
Quick answer
Noble gases are the Group 18 elements whose outer shells are already full, so they barely react.
Definition
The noble gases — helium, neon, argon, krypton, xenon and radon — close Group 18 with completely full outer shells: eight electrons each, except helium's snug pair. With nothing to gain and nothing to shed, they exist as lone atoms and react only grudgingly, which earned them the nickname inert gases. Argon is the quiet achiever of air, about 0.93% of every breath. Their fullness is the yardstick of chemistry: other elements react precisely to reach a noble gas shell arrangement of their own.
For example
A party balloon floats on helium, and an old filament bulb keeps its tungsten alive inside argon — the gas refuses to let the hot metal burn.