The table below shows the approximate percentages of carbon dioxide, nitrogen, and oxygen in the Earth's early atmosphere compared to today's atmosphere.
| Gas | Approximate percentage in the early atmosphere | Percentage in today's atmosphere |
|---|---|---|
| Carbon dioxide | 95% | 0.04% |
| Nitrogen | 4% | 78% |
| Oxygen | 0% | 21% |
Over billions of years, natural processes have significantly changed the percentages of these gases.
Explain how the percentage of each of these three gases in the atmosphere changed to reach their current levels.
97 exam-style questions on Edexcel GCSE Chemistry 9.2 Earth and atmospheric science, covering 9.2.1 The Earth's early atmosphere, 9.2.2 How the atmosphere evolved, 9.2.3 Chemical test for oxygen, and 9.2.4 The greenhouse effect and climate change. Each one has a worked solution and a mark scheme showing where the marks go.