Question

Which of the following is the third most abundant gas in the Earth’s atmosphere?
a.) Carbon
b.) Nitrogen
c.) Oxygen
d.) Neon
e.) Argon

Answer 1

Hint: Compounds of this element are rarely encountered due to the inertness of the atom. However, these compounds have been detected in inert gas matrix isolation, cold gases, and plasmas, and molecular ions containing argon have been made and also detected in space.

Step-by-Step Solution:
The atmosphere is a mixture of gases that surround the Earth. It is essential to all life and serves several purposes, such as providing air for respiration, absorbing harmful ultraviolet radiation, protecting the earth from falling meteorites, controlling climate and regulating the water cycle.
Let us eliminate Carbon as a possible answer straight off the bat, as while some organic compounds of Carbon can exist in the atmosphere as gases, elemental Carbon in its purest form is mostly found in nature as a solid substance.
Now, let us analyse the composition of the atmosphere to help us answer this question.
The most abundant gas in the atmosphere is nitrogen. The Earth’s atmosphere is composed of approximately 78 percent nitrogen, 21 percent oxygen, 1 percent argon and trace amounts of other gases that include carbon dioxide and neon.
Therefore, by this analysis, we can safely conclude that the third most abundant gas in the atmosphere and by extension, the answer to this question, is e) Argon.

Note: While it is often easy to be confused between the compositions of Argon and Water Vapour in the atmosphere, remember that Argon is more than twice as abundant as water vapor (which averages about 4000 ppmv, but varies greatly), 23 times as abundant as carbon dioxide (400 ppmv), and more than 500 times as abundant as neon (18 ppmv). Argon is the most abundant noble gas in Earth's crust, comprising 0.00015% of the crust.