The primary chemical composition of Earth's atmosphere includes nitrogen (approximately 78%), oxygen (around 21%), with trace amounts of carbon dioxide, argon, and other gases. This mixture is essential for sustaining life, as oxygen supports respiration in living organisms, while nitrogen is a critical component of biological molecules like proteins and nucleic acids. The presence of greenhouse gases like carbon dioxide is also vital in regulating the planet's temperature through the greenhouse effect. Understanding this composition is crucial for addressing climate change and air quality issues.