The atmosphere has been relatively stable for the last 200 million years:
- Nitrogen (N₂) — About 78%. Unreactive gas; released from volcanoes and denitrifying bacteria
- Oxygen (O₂) — About 21%. Produced by photosynthesis; essential for aerobic respiration
- Argon (Ar) — About 0.9%. Noble gas, extremely unreactive
- Carbon dioxide (CO₂) — About 0.04%. Currently increasing due to human activities
- Water vapour — Variable (~1–4%). Depends on temperature and location
Memory key: 78-21-1 = Nitrogen-Oxygen-Argon (NOA)
This key facts covers Current Atmospheric Composition within Composition of Atmosphere for GCSE Chemistry. Revise Composition of Atmosphere in Atmosphere for GCSE Chemistry with 20 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 4 of 13 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Composition of Atmosphere
What is the approximate percentage of nitrogen in the current atmosphere?
Describe how Earth's early atmosphere was formed.
Quick recall flashcards
What percentage of the atmosphere is CO₂?
About 0.04%
How was oxygen added to the atmosphere?
Photosynthesis by plants and algae