What are the main components of the Earth's atmosphere?

The primary components of the Earth's atmosphere are nitrogen and oxygen. Nitrogen makes up about 78% of the atmosphere, while oxygen accounts for approximately 21%. These two gases are essential for life on Earth; oxygen is crucial for respiration in most living organisms, while nitrogen plays a key role in the biological processes and is part of the proteins and nucleic acids necessary for life.

While other gases, such as carbon dioxide and trace amounts of hydrogen, do exist in the atmosphere, they are not the primary components. Carbon dioxide, for instance, is present in much smaller quantities (around 0.04%) and is important for processes like photosynthesis, but it does not dominate the composition of the atmosphere as nitrogen and oxygen do. Thus, the selection of nitrogen and oxygen accurately reflects the most significant elements that make up the air we breathe and are essential for ecological balance on Earth.