Question

The elements with atomic numbers 2, 10, 18, 36, 54 and 86 are collectively known as:
(A) Alkaline earth metals
(B) Inert gas
(C) Halogens
(D) Rare earths

Answer 1

Hint: All the elements of the given atomic number are present in the group-18 of the periodic table. They have eight electrons in their valence shell. All the given elements are gases.

Complete step by step answer:
We are given the atomic numbers of certain elements and we need to tell the collective name which they are known as. In order to find the name, we will first need to find out the name of the elements to get the better idea.
The name, chemical symbol of the elements with given atomic numbers are as below.

Atomic number	Element	Chemical symbol
2	Helium	He
10	Neon	Ne
18	Argon	Ar
36	Krypton	Kr
54	Xenon	Xe
86	Radon	Rn

- As we see the characteristics of all the given elements, we can say that they are inert gases. They are also known as noble gases.
- They have exceptional stability and they do not react with any element. They exist as a single atom in their molecular form. That is the reason why they are known as inert gases. They all are found in gaseous form.
- The reason behind their stability is their electronic configuration. They have a complete octet configuration in their valence shell. So, they neither donate or accept nor share any electrons with other elements. So, we can conclude that the elements with given atomic numbers are collectively known as inert gases.
So, the correct answer is “Option B”.

Note: In terms of reactivity of the inert gases, Xenon is an exception. Xenon can form some stable compounds which includes $Xe{F_2}$, $Xe{O_4}$, $XeO{F_4}$, etc. All the inert gases are colorless, odorless and monatomic gases.