What percentage of Earth's atmosphere is composed of nitrogen?

The atmosphere of Earth is predominantly composed of nitrogen, making up about 78% of its total composition. This significant presence of nitrogen is crucial because it plays a foundational role in the atmosphere, providing stability and influencing various environmental processes. Nitrogen, being an inert gas under normal conditions, does not react readily with other substances, which helps maintain the overall balance of the atmosphere.

In relation to the other choices, 21% refers to the percentage that oxygen contributes to the atmosphere, which is essential for supporting life. The figure of 1% represents trace gases and water vapor, which are present in much smaller amounts, and 50% does not accurately reflect any major component of the atmosphere. Understanding the exact percentages is important as it reflects the balance of gases necessary for life and weather patterns on Earth.