Which gas makes up the majority of Earth's atmosphere?

• A. Argon (Ar)
• B. Nitrogen (N_2)
• C. Carbon dioxide (CO_2)
• D. Oxygen (O_2)

Answer: (B)

Verified step by step guidance

1. Understand that Earth's atmosphere is composed of several gases, each present in different proportions.
2. Recall that the major components of dry air are nitrogen (N\_2), oxygen (O\_2), argon (Ar), and carbon dioxide (CO\_2), among others in trace amounts.
3. Identify that nitrogen (N\_2) makes up the largest percentage of the atmosphere, approximately 78% by volume.
4. Recognize that oxygen (O\_2) is the second most abundant gas, making up about 21%, followed by argon and carbon dioxide in much smaller amounts.
5. Conclude that the gas making up the majority of Earth's atmosphere is nitrogen (N\_2).