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Nitrogen is the most abundant gas in Earth's atmosphere. It makes up about 78% of the air we breathe. As a crucial component, nitrogen is essential for creating proteins in plants and animals.
In its gaseous form, nitrogen is relatively inert. This means it doesn't react easily with other substances. This stability allows it to play a key role as a filler gas in the atmosphere. It contributes to the balance of gases that sustain life on Earth without participating in chemical reactions itself.
Although nitrogen is not directly used in respiration, it has interesting roles. For example, it provides a consistent pressure in the atmosphere. It's also critical to the nitrogen cycle, where nitrogen gets fixed into a form that plants can use to grow. Once taken up by plants, it moves through the food chain, supporting all living organisms.

Oxygen is vital for most living organisms on Earth. It accounts for about 21% of the atmospheric gases. It plays a crucial role in the process of respiration, which is the way organisms convert the energy stored in food into usable energy.
During respiration, oxygen is inhaled and then used by cells to break down food molecules. This process releases energy, carbon dioxide, and water as byproducts. Oxygen is equally essential for combustion. It supports the burning of fuels, which is useful in several industrial and domestic applications.
In addition to its critical biological functions, oxygen also forms ozone in the upper atmosphere. Ozone is important because it absorbs harmful ultraviolet radiation from the sun, protecting living organisms on Earth from potential damage.

Argon, while less talked about, is the third most prevalent gas in the Earth's atmosphere. It constitutes about 0.93% of the air. Although it does not have a direct role in biological processes like nitrogen or oxygen, argon is significant in other areas.
This noble gas is completely inert, which means it is very stable and doesn’t react under most conditions. Due to this property, argon is often used in environments where materials need to be kept free from reacting with the surrounding air, such as in welding or in preserving historical documents.
Argon's stability as a gas means it serves as a terrific shield gas in industrial processes. Its non-reactive nature also makes it valuable in the science field, where maintaining a controlled environment is critical.