In what form does nitrogen primarily exist in Earth's atmosphere?

• A. NH_3 (ammonia)
• B. N (atomic nitrogen)
• C. NO_2 (nitrogen dioxide)
• D. N_2 (diatomic nitrogen gas)

Answer: (D)

Verified step by step guidance

1. Recall that Earth's atmosphere is composed mainly of gases, with nitrogen being one of the most abundant elements present.
2. Understand that nitrogen in the atmosphere is not typically found as single atoms (N) because atomic nitrogen is highly reactive and unstable under normal atmospheric conditions.
3. Recognize that nitrogen does not primarily exist as compounds like ammonia (NH_3) or nitrogen dioxide (NO_2) in the atmosphere, as these are present only in trace amounts and are usually products of biological or industrial processes.
4. Identify that nitrogen primarily exists as a diatomic molecule, meaning two nitrogen atoms are bonded together, forming N_2, which is a very stable and inert gas under atmospheric conditions.
5. Conclude that the correct form of nitrogen in Earth's atmosphere is N_2 (diatomic nitrogen gas), which makes up about 78% of the atmosphere by volume.