Question

__________ is a radioactive inert gas.

Answer 1

Hint: The inert gas which is at the bottom of the periodic table in the group-18 shows radioactivity. The valence shell of that gas has a principal quantum number of 6. Inert gases are also called noble gases.

Complete step by step answer:
- Inert gases are the gases that are arranged in the group-18 of the periodic table.
- All the inert gases have eight electrons in their valence shell. So, they have a complete octet configuration. Their valence orbital is the p-orbital.
- Due to their complete octet electronic configuration. That is the reason why they are inert and do not react with other compounds.
- Radioactivity is the phenomenon shown by some unstable atoms which have imbalance in the number of protons and neutrons present in the nucleus and due to this, the atom releases energy in certain periods of time.
- Generally the atoms which are situated at the bottom of the periodic table or the ones which have higher atomic number show radioactivity. Let’s see all the inert gases present in the periodic table.

Gas	Atomic number
Helium (He)	2
Neon (Ne)	10
Argon (Ar)	18
Krypton (Kr)	36
Xenon (Xe)	54
Radon (Rn)	86

- Out of them, the gas with the highest atomic number, Radon shows radioactivity. No other inert gases are radioactive.
Thus, we can say that Radon (Rn) is a radioactive inert gas.

Note: Generally the element that has high difference between the numbers of protons and neutrons present in the nucleus of the atom has higher chances to be radioactive. Remember that the chemical symbol of Radon is Rn. The main radioactive isotopes of Radon have atomic mass of 210, 211, 222 and 224$gmmo{{l}^{-}}$.