The main gas found in the Earth's atmosphere is nitrogen, which constitutes approximately 78% of the atmosphere by volume. Following nitrogen, oxygen is the second most abundant gas, making up about 21%. The remaining percentage consists of trace gases such as argon, carbon dioxide, and others. Nitrogen plays a crucial role in maintaining atmospheric pressure and supporting life on Earth, while oxygen is essential for respiration in most living organisms. The balance of gases in our atmosphere is vital for sustaining ecosystems and regulating the planet's climate.