The most abundant gas in Earth’s atmosphere is nitrogen. It comprises about 78% of the atmosphere by volume. This dominance of nitrogen in our atmosphere is a result of various processes that have occurred over billions of years, shaping the unique composition of Earth’s atmosphere.
Nitrogen, as a molecule, is relatively inert under normal conditions. Its stability is due to the strong triple bond between the two nitrogen atoms in the N2 molecule. Because of its inert nature, nitrogen does not easily react with other elements or compounds, which is one reason why it has accumulated in such large amounts in the atmosphere.
Interestingly, while nitrogen is overwhelmingly abundant in the atmosphere, it’s often in a form that is not directly usable by most organisms. For life, particularly plants, to utilize nitrogen, it usually needs to be “fixed” or converted into a more reactive form. This process is carried out by certain bacteria and lightning in the atmosphere. These fixed forms of nitrogen can then be taken up by plants and, in turn, enter the food chain.
Following nitrogen, the second most abundant gas in our atmosphere is oxygen, constituting about 21% by volume. Oxygen plays a critical role in the respiration of many organisms, including humans, and is vital for the combustion processes that power many of our technologies.
Other gases, often referred to as trace gases, make up the remaining 1% of the atmosphere. These include argon, carbon dioxide, neon, and other trace gases. It’s worth noting that while some of these gases, like carbon dioxide, are present in small amounts, their roles in processes such as the greenhouse effect are profound.
In summary, nitrogen’s dominance in the atmosphere is a result of its stable molecular structure and the complex interplay of geological and biological processes over eons.