Which is the most abundant element in the Earth’s atmosphere?

The most abundant element in the Earth’s atmosphere is Nitrogen (N₂). Nitrogen constitutes approximately 78% by volume of the atmosphere, making it the dominant component of air. It is a diatomic molecule, meaning each nitrogen molecule consists of two nitrogen atoms, and it is largely inert under standard temperature and pressure.

Nitrogen plays a crucial role in both chemistry and biology. In the atmosphere, its chemical stability helps maintain a non-reactive environment, preventing rapid combustion and oxidation that could occur if oxygen were the only major component. In nature, nitrogen is essential for life, as it is a major component of amino acids, proteins, and nucleic acids in plants and animals.

In contrast, oxygen (O₂) is the second most abundant element in the atmosphere at around 21%, which is vital for respiration and combustion. Hydrogen is very rare in the atmosphere because it is light and escapes Earth’s gravity easily. Nickel is a metal found mostly in the Earth’s crust and is not a significant atmospheric component.

Nitrogen cycles through the environment via the nitrogen cycle, which includes processes such as nitrogen fixation, nitrification, denitrification, and ammonification. Atmospheric nitrogen is converted by bacteria and lightning into reactive compounds like ammonia (NH₃) and nitrates (NO₃⁻), which are essential nutrients for plants.

Because of its abundance and chemical properties, nitrogen is widely used in industry and science. It is employed in the production of fertilizers, explosives, and chemical reagents, and it is used to create inert atmospheres in laboratories and food packaging to prevent oxidation.

Therefore, the correct answer is Nitrogen (Option A), as it is the most abundant element in Earth’s atmosphere, accounting for nearly four-fifths of the air we breathe.