Question

Least chemical activity is shown by
A) Nitrogen
B) Argon
C) Methane
D) Ammonia

Answer 1

Hint: The chemical activity of an element is decided by the count of valence electrons of an atom. If the valence electron count is 2 or 8, that means the orbit is fully filled, so, in that case, reactivity is less.

Complete Step by Step Solution:
Let's discuss the reactivity of noble gases. They are the elements that belong to the last group of the periodic table. They possess a fully filled outermost shell. Some examples of noble gases are helium, neon, argon, xenon, Krypton, etc. As their valence shell is complete, their reactivity is less. Therefore, they are called inert gases.

Let's discuss argon in detail. Argon belongs to the class of noble gas positioned in the periodic table's 18^th group. And it is the noble gas that is abundant on earth. It is 0.00015% of the crust. Its atomic number is 18 and its configuration is 2,8,8. So, it has completely filled the outermost shell. So, its reactivity is less.

Let's discuss other options one by one. Nitrogen is a non-metal and it is reactive in nature as it requires three more electrons to attain stability. Methane and ammonia are also reactive compounds.
Therefore, among the given options, argon is the least reactive.
Hence, option B is right.

Note: Only xenon, among the noble gases, forms a large number of compounds with oxygen and fluorine. This is because of the larger size of the xenon atom. And, due to the large size, there is a weak attraction of the electrons to the nucleus and this helps in compound formation.