Nitrogen (N₂)

Nitrogen makes up the majority of dry air, constituting about 78% of the atmosphere by volume. It is a diatomic molecule composed of two nitrogen atoms.

Oxygen (O₂)

Oxygen is the second most abundant gas in dry air, comprising approximately 21% of the atmosphere. It is essential for the respiration of many organisms, including humans.

Argon (Ar)

Argon is a noble gas that makes up about 0.93% of dry air. It is chemically inert and does not readily react with other elements.

Carbon Dioxide (CO₂)

Carbon dioxide is a trace gas in dry air, making up about 0.04%. While it is a minor component, it plays a crucial role in the Earth's carbon cycle and contributes to the greenhouse effect.

Neon (Ne), Helium (He), Krypton (Kr), Xenon (Xe)

These noble gases, along with argon, are present in very small amounts in dry air. They are chemically inert and do not participate in most chemical reactions.

Notably, dry air does not contain water vapor. Water vapor is the gaseous state of water, and its presence in the atmosphere is variable and depends on factors such as temperature and humidity. Dry air is often considered in contrast to humid air, which contains a significant amount of water vapor.

The composition of dry air is relatively constant at sea level but can vary at higher altitudes or in different geographic locations. The standard composition, often referred to as "dry air" for practical purposes, serves as a baseline for understanding atmospheric gases and their interactions.