What is the composition of Earth's atmosphere in terms of nitrogen percentage?

The composition of Earth's atmosphere is primarily characterized by nitrogen, which constitutes about 78% of the total atmosphere. This significant percentage makes nitrogen the most abundant gas in the atmosphere. It plays a crucial role in various natural processes, including the nitrogen cycle, which is vital for sustaining life. Nitrogen is an inert gas under normal conditions, meaning it does not readily react with other substances, allowing it to remain a stable component of the atmospheric mixture.

To understand why the other choices do not accurately reflect the atmospheric composition: 21% refers to oxygen, which is the second most abundant gas. The figure of 0.03% pertains to carbon dioxide, which is present in very small amounts and plays a critical role in climate regulation and photosynthesis. The 1% reference likely indicates other trace gases, but these are minimal compared to nitrogen. The large proportion of nitrogen contributes to the overall stability and structure of the atmosphere, making it essential for various ecological and biological functions.