Nitrogen in the Air and in Compounds — N2

N₂ = diatomic nitrogen molecule. Dry air ≈ 78% N₂ by volume (O₂ ≈ 21%). Bonding: N≡N triple bond → large energy to break → inert as an element. Exam focus here is the free element in air — not yet the full compound list (NH₃, HNO₃, …).

This topic isolates nitrogen as it exists in the atmosphere. Diatomic molecule. Nitrogen gas is N₂, not free N atoms. Two nitrogen atoms share a triple bond. Abundance. About 78% of dry air by volume is N₂ — the majority gas students should name first, not oxygen. Inertness. The N≡N triple bond is very strong. Breaking it needs a large energy input, so N₂ is reluctant to react at room temperature with most substances. That is why the sky can be full of nitrogen while organisms still need combined nitrogen (fixation, fertilisers). Link forward (one line only). Industrial Haber later forces N₂ into NH₃; this page’s job is percentage + diatomic + triple-bond inertness. Do not fill this answer with Ostwald, Contact, or long oxide lists unless asked — those are sister topics.

Air is mostly nitrogen gas written N₂ — about 78%. N₂ means two nitrogen atoms joined together. They are held by a strong triple bond, so N₂ does not react easily.

State “~78% of dry air is N₂”, name the molecule as diatomic, and give N≡N as the reason for inertness. Contrast briefly with oxygen (~21%) so the percentage is not confused. Mention that inertness explains the need for nitrogen fixation without writing the full Haber plant.

Connect high bond enthalpy of N≡N to high activation energy for many N₂ reactions under ordinary conditions. Keep oxidation-state note light: N in N₂ is 0 until fixed into compounds. In longer answers, distinguish physical abundance of N₂ from biological availability of combined nitrogen.

N₂ diatomic · ~78% dry air · N≡N triple bond → inert. Not O₂ as the majority gas.