Question

Which one of the following is not a noble gas?
${\text{A}}{\text{.}}$ Helium
${\text{B}}{\text{.}}$ Xenon
${\text{C}}{\text{.}}$ Radium
${\text{D}}{\text{.}}$ Radon

Answer 1

Hint- Here, we will proceed by the orientation of noble gases in the periodic table along with their names. Then, we will discuss chemical inertness of these gases for making compounds.

Complete answer:
The noble gases are a group of chemical elements on the periodic table which make up Group 18. Under normal conditions, these gases all have similar properties i.e., they are all odourless, colourless, monatomic gases of very low chemical reactivity. The six naturally occurring noble gases are helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn).
Modern theories of atomic structure can well clarify the properties of the noble gases. The outer shell of valence electrons is considered to be “full” in noble gases, giving them little tendency to participate in chemical reactions.
The noble gasses have weak interatomic strengths and therefore have very low melting and boiling points. They are all monatomic gases under standard conditions, including those with larger atomic masses than many other elements that are solids under standard conditions.
The noble gas atoms, as do the atoms on the periodic table in most other groups, rise steadily in the atomic radius from one period to the next due to an increasing number of electrons. The size of the atom is related to several properties. For example, the ionization potential decreases with an increasing radius due to the fact that the valence electrons in the larger noble gasses are farther away from the nucleus and hence the atom does not hold together as tightly. Noble gases possess the largest ionization potential among the elements of each time. This represents their electron configuration 's stability, and points again to their relative lack of chemical reactivity.
Originally, the noble gases were also referred to as "inert gases," since compounds were believed to not react with other elements. Because the heavier noble gas atoms are bound together less strongly by electromagnetic forces than are the lighter noble gases, such as helium, it is easier to detach the outer electrons of these heavier atoms. This is why several compounds of the xenon, krypton, and radon gases can actually be formed. Among the six noble gasses, only krypton, xenon, and radon are capable of forming stable compounds. Such agents are used as oxidizers.
Therefore, radium is not a noble gas.

Hence, option C is correct.

Note- Radium (Ra) is referred to as a radioactive chemical element which is the heaviest of all the alkaline earth metals of Group 2 of the periodic table. A silvery white metal that does not occur free naturally is called radium. The most important use of radium was principally for the treatment of cancer by subjecting tumours to the gamma radiation of its daughter isotopes.