Question

Why isn't Earth's atmosphere mostly hydrogen?

Answer 1

Earth's atmosphere is not mostly hydrogen because hydrogen molecules can escape into space due to their low mass compared to other gas molecules.

Step-by-step explanation:

The reason Earth's atmosphere is not mostly hydrogen is because hydrogen molecules can reach speeds above Earth's escape velocity and escape into space. This is due to their lower mass compared to other gas molecules such as nitrogen and oxygen. Over billions of years, more hydrogen molecules have escaped from the atmosphere than other molecules, resulting in a low abundance of hydrogen in Earth’s atmosphere.

Answer 2

...... because hydrogen moves faster than heavier gases and escapes from the earth's gravitational field.