Nitrogen in Earth's atmosphere
Earth's atmosphere is a mixture, not a single gas. Nitrogen is its largest component; oxygen, argon, carbon dioxide, water vapor, and trace gases make up the rest.
What 78 percent means
Dry air near the surface is about 78% nitrogen and 21% oxygen by volume, with argon and other gases making up most of the remainder. Water vapor varies with weather, so percentages depend on whether it is included.
A reservoir above us
Most atmospheric nitrogen is N₂. Atoms enter ecosystems through fixation and other pathways, then return through processes including denitrification. Concentrated nitrogen can displace oxygen in enclosed areas without a reliable sensory warning.
Sources and further reading
These references are starting points. Check the source directly for definitions, dates, units, and context. This is an educational overview, not an operating manual or professional advice.
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