What is, by far, the most abundant component of Earth's atmosphere?

Molecular Nitrogen

Explanation:

Earth's atmosphere is a mixture of several gases in their molecular form. The most abundant of them is the element nitrogen. 78% of it is nitrogen and the rest that follow are Oxygen, Carbon dioxide and a mixture of other gases like Neon, Helium, Methane, Water vapor. hen the air is dry, argon is the third most abundant element in the earth's atmosphere.

As the height above the earth's surface increases, the air molecules decrease.