When nitrogen and oxygen are present in the atmosphere, the primary molecule nitrogen is found in is nitrogen gas (N₂).

Here's why:

* Nitrogen is diatomic: Nitrogen naturally exists as a diatomic molecule, meaning two nitrogen atoms bond together (N₂).

* Atmospheric abundance: Nitrogen gas makes up about 78% of the Earth's atmosphere.

* Reactivity: While nitrogen is essential for life, it's relatively unreactive at normal temperatures and pressures. It takes a lot of energy to break the strong triple bond between the nitrogen atoms in N₂.

While nitrogen can form other compounds in the atmosphere, like nitrogen oxides, these are typically present in much lower concentrations than N₂.