Air and Atmosphere - Properties and Uses of Oxygen and Nitrogen

Air is a mixture of gases. Nitrogen ($N_2$) accounts for approximately $78\%$, Oxygen ($O_2$) accounts for $21\%$, and the remaining $1\%$ consists of Carbon dioxide ($CO_2$), Argon ($Ar$), water vapor, and dust particles.

Oxygen ($O_2$) is a colorless, odorless, and tasteless gas. It is slightly heavier than air and slightly soluble in water, which allows aquatic organisms to breathe dissolved oxygen.

Oxygen is a strong supporter of combustion (burning) but is not flammable itself. It reacts with metals to form basic oxides, such as Magnesium Oxide ($MgO$), and with non-metals to form acidic oxides, such as Sulfur Dioxide ($SO_2$).

Nitrogen ($N_2$) is a relatively inactive gas at room temperature. Its primary role in the atmosphere is to dilute the activity of oxygen, preventing rapid combustion and controlled respiration rates.

The 'Nitrogen Cycle' is essential for life, as nitrogen is a key component of proteins. While plants cannot absorb $N_2$ directly from the air, it is converted into nitrates in the soil through lightning and nitrogen-fixing bacteria.

Rusting is a slow chemical reaction where Iron ($Fe$) reacts with Oxygen ($O_2$) and moisture ($H_2O$) to form hydrated iron (III) oxide ($2Fe_2O_3 \cdot xH_2O$).