Question

The third most abundant gas in Earth's atmosphere is:
A. Carbon
B. Nitrogen
C. Oxygen
D. Argon

Answer 1

Hint: Any element or gas which is present in plenty in the atmosphere is called an abundant element or gas. Abundant element or gas has so many main sources for its presence.

Complete step by step answer:
> As we know carbon exits as carbon dioxide gas($\text{C}{{\text{O}}_{2}}$). It is present in Earth's atmosphere at a low concentration and it also acts as greenhouse gas. In the solid state it is called dry ice. The current concentration of carbon dioxide is 0.04% in earth's atmosphere. The main source of Carbon dioxide are:
Ocean release and respiration , human sources come from activities like cement production, deforestation as well as the burning of fossil fuels like coal, oil and natural gas are also its main source.
> Nitrogen (${{\text{N}}_{2}}$) gas is a colorless, odorless and tasteless gas. It is nonflammable and it doesn't support any combustion. It accounts for 78% of the atmosphere. The main sources of Nitrogen gas are: Atmospheric precipitation, geological sources, agricultural land, livestock and poultry operations and urban waste .
> Oxygen is the third most abundant element in the universe and the most abundant element by mass in the earth's crust. It exists as ${{\text{O}}_{2}}$ gas and constitute about$\text{20}\text{.9 }\!\!%\!\!\text{ }$ of the volume of air.
The main sources of oxygen are: Breathing of plants and animals and decomposition of dead plant and animal material.
> Argon is Colorless, odourless, non-reactive, inert gas. It accounts for $0.93%$ vol.
The main source of argon gas is: Decay of potassium -40 in the earth crust.
So from above, we can conclude that argon is the third most abundant gas in the Earth's atmosphere therefore, option D is correct.

Note: Always try to remember the percentage volume of top-4 abundant gases. The composition of the air in earth's atmosphere is: nitrogen — 78 percent; oxygen — 21 percent; argon — 0.93 percent; carbon dioxide — 0.04 percent and some amounts of neon, helium, methane, krypton and hydrogen, as well as water vapor are also present.