Question

Noble gases or inert gases are so named because they are highly unreactive and do not form compounds under normal conditions. Which of these is not an inert gas?
A. Xenon
B. Radon
C. Oganesson
D. Zirconium

Answer 1

Hint:We know that Noble gases are placed in Group $18$ also known as Group $0$ of the periodic table hence their valence shell is complete. Each noble gas is placed between the most electronegative elements also known as the halogen elements $\rm{(Group\,17)}$ and the most electropositive elements or alkali elements $\rm{(Group\,1)}$.

Complete answer:
We know that the valence shell of the noble gases is completely filled so they are highly stable. Because of having its octet complete and a high stability it is chemically inert or unreactive or we can say that these elements do not combine with other elements to form a compound. Hence as they do not combine so they occur as monoatomic molecules which means that one molecule of noble gas will contain only one atom.
There are a total seven noble gases in the periodic table. They are Helium, Radon, Neon, Xenon, Argon, Krypton and Oganesson.
Hence, we see that Zirconium is not a noble gas. Zirconium is a transition element which belongs to the Group \[4\] of the periodic table. It is not an inert gas as its octet is not complete and so it is not so stable. Also, Zirconium is less reactive at room temperature but becomes reactive with non-metals when the temperature is increased.

So, the correct answer is option D.

Note:
Oganesson is predicted to be a noble gas but it has still not been chemically investigated. Also, it is not fully true that noble gases do not form compounds, some of them do form compounds with other elements. For example, Xenon forms a compound with fluorine as Xenon is large in size so there is a weak force of attraction between the electrons and the nucleus.