Final answer:
Atmospheric air is primarily made up of nitrogen (78.6%) and oxygen (20.9%), with smaller amounts of argon, carbon dioxide, water vapor, and trace gases. The atmospheric pressure is made up of the sum of the partial pressures of each individual gas component.
Step-by-step explanation:
The atmosphere that we breathe is a complex system of gases that supports life on Earth. It is comprised primarily of nitrogen (N₂; 78.6 percent) and oxygen (O₂; 20.9 percent). Other significant components include argon (Ar; about 0.9 percent), and carbon dioxide (CO₂; 0.04 percent). The atmosphere also consists of variable amounts of water vapor (H₂O), methane, neon, helium, and other trace gases. The atmospheric air's composition is remarkably uniform below about 100 km altitude.
Each gas in the atmosphere contributes to the overall atmospheric pressure, exerting its own partial pressure. This partial pressure can be calculated by the formula P = (Patm) X (percent content in mixture). For example, oxygen's partial pressure is much higher than that of carbon dioxide, due to its greater abundance in the air.