Question

Which one of the following noble gases is not found in the atmosphere?
A.Argon
B.Krypton
C.Radon
D.Xenon

Answer 1

Hint: We must know that the nature of noble gases and radon is derivative of radium and is artificially made inert gas.



Complete step by step solution:
We must remember that the noble gases are a group of highly unreactive or inert elements that are placed in the Group 18 in the periodic table. Helium(He), neon(Ne), argon(Ar), krypton(Kr), xenon(Xe), and radon(Rn) are the noble gases, in order of their increasing density values. They are called noble gases because they do not react with other chemicals. Due to this, they are also known as inert gases.
All noble gases are present in Earth's atmosphere except helium and radon.
Radon is not naturally occurring in the atmosphere. Radon is generated by the radioactive decay of radium-226, which is found in uranium ores. It is a radioactive element with a half-life of 3.8 days.
Out of the noble gases, Argon is comparatively abundant in concentration in the atmosphere, near about 1% of atmospheric air. Remaining noble gases are present in negligible amounts. The concentration of Neon is 20 ppm, krypton is 1 ppm and xenon 0.1 ppm.
The concentration of radon in the atmosphere is approximately\[6 \times {10^{ - 18}}\] molar percent or about 150 atoms per ml of air.
So, Radon from the given noble gases is not found in the atmosphere naturally.
Hence, the correct option is option ‘C’


Note: Actually, Radon concentrations that occur in natural environments are too low to be detected by chemical methodology. Radon concentration in the atmosphere is usually measured in becquerel per cubic meter\[\left( {Bq/{m^3}} \right)\]. One Becquerel unit is equal to one radioactive disintegration per second.