Atmosphere
Definition and meaning of Atmosphere in chemistry.
The atmosphere is the layer of gases surrounding Earth held in place by gravity, consisting primarily of nitrogen, oxygen, argon, and carbon dioxide. It regulates climate, protects life from harmful radiation, and enables chemical reactions essential to life.
In more detail
The atmosphere consists of multiple layers with distinct properties: the troposphere (where weather occurs), stratosphere (containing the protective ozone layer), mesosphere, and thermosphere. Chemical reactions constantly occur, including photochemistry driven by solar ultraviolet radiation, which converts oxygen molecules into protective ozone. Atmospheric composition also affects climate, greenhouse gases trap thermal energy and regulate Earth's temperature. Human activities have significantly altered atmospheric chemistry through emissions of carbon dioxide, methane, and industrial pollutants.
Key facts
| Field | Physical Chemistry |
|---|---|
| Primary composition | Nitrogen (N2) ~78%, Oxygen (O2) ~21%, Argon (Ar) ~0.93%, Carbon Dioxide (CO2) ~0.042% |
| Protective layer | Ozone (O3) in the stratosphere absorbs ultraviolet radiation |
| Temperature gradient | Decreases with altitude in the troposphere at ~6.5°C per kilometer |
The stratosphere contains the ozone layer, where oxygen molecules (O2) absorb intense solar ultraviolet radiation and form ozone (O3), which shields Earth's surface from harmful UV exposure that would damage DNA in living organisms.
Frequently asked questions
What is the most abundant gas in Earth's atmosphere?
Nitrogen (N2) comprises approximately 78% of the atmosphere. Although oxygen (O2) is vital for aerobic respiration, it makes up only about 21%.
Why is the ozone layer important?
Ozone (O3) in the stratosphere absorbs ultraviolet radiation from the sun, preventing most UV-B and UV-C radiation from reaching Earth's surface. Without this protective layer, solar radiation would cause severe damage to life forms.