AP BIOLOGY

Detailed explanation-1: -The most abundant naturally occurring gas is nitrogen (N2), which makes up about 78% of air. Oxygen (O2) is the second most abundant gas at about 21%. The inert gas argon (Ar) is the third most abundant gas at 0.93%.

Detailed explanation-2: -Earth’s atmosphere is composed of about 78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, and 0.1 percent other gases.

Detailed explanation-3: -Oxygen is a major component of the solid earth, along with Si and elements such as Mg, Ca and Na. Nitrogen is not stable as a part of a crystal lattice, so it is not incorporated into the solid Earth. This is one reason why nitrogen is so enriched in the atmosphere relative to oxygen.

Detailed explanation-4: -By far, the most abundant gas in the Earth’s atmosphere is nitrogen, which accounts for about 78% of the mass of dry air. Oxygen is the next most abundant gas, present at levels of 20 to 21%.

Detailed explanation-5: -The abundance of gases in the atmosphere in the decreasing order is as follows: nitrogen, oxygen, argon, water vapour, carbon dioxide. Hence nitrogen constitutes 78% of the atmospheric air and is the most abundant gas in the atmosphere.