Air, a mixture of gases, forms the Earth’s atmosphere. This invisible blanket is fundamental to life. Understanding its components reveals the intricate chemical balance of our environment. The atmosphere is primarily composed of several stable gases, alongside other variable elements and microscopic particles.
The Primary Gaseous Components
Dry air consists overwhelmingly of two main gases: nitrogen and oxygen. Nitrogen (N₂) makes up approximately 78.08% of dry air by volume. This elemental gas is colorless, odorless, and tasteless. Nitrogen is also largely inert, not readily reacting with other substances under normal atmospheric conditions.
Oxygen (O₂) is the second most abundant gas, accounting for about 20.95% of dry air. Like nitrogen, oxygen is a colorless, odorless, and tasteless gas. It is denser than air and plays a role in various chemical processes, including combustion.
Argon (Ar) is the third most abundant gas in dry air, present at about 0.93%. As a noble gas, argon is chemically inert. It is also colorless, odorless, and tasteless.
Lesser Abundant Gases
Beyond the primary components, other gases exist in smaller quantities within the atmosphere. Carbon dioxide (CO₂) typically makes up about 0.04% of dry air. Its concentration has reached approximately 427 parts per million (ppm), a significant increase of 50% since the Industrial Revolution.
Trace noble gases also contribute to the atmosphere’s composition in much smaller amounts. These include neon (Ne), helium (He), krypton (Kr), and xenon (Xe). These gases are unreactive and are present as individual atoms.
Other Atmospheric Components
In addition to stable gaseous components, air also contains variable and non-gaseous elements. Water vapor (H₂O) is a highly variable gaseous component, with its concentration fluctuating based on location, temperature, and weather conditions. At sea level, water vapor can average around 1% of the atmosphere, but its presence can range from nearly 0% to as much as 5% in hot, humid air masses.
The atmosphere also contains particulate matter, which are solid or liquid particles suspended in the air. These include natural components such as dust, pollen, and spores. Dust originates from soil blown by winds, while pollen and spores are biological particles released by plants and fungi. Other atmospheric particles, known as aerosols, come from natural sources like sea spray or volcanic ash.