Explain why the elements nitrogen, oxygen, and hydrogen are often found in both the Earth's atmosphere and crust.

The Earth's atmosphere that we know today originated millions of years ago when volcanic activity released materials from the Earth's crust. These were mainly: H2O, CO2, N2, and sulfates. Through the passage of time and adjustments in the atmosphere, a lot of CO2 was converted by plants and algae into oxygen, while N2 remained because it is inert.