Definition: Oxygen in the atmosphere is the second most abundant gas in the atmosphere behind nitrogen. Oxygen makes up 29.047% of the atmosphere by volume in dry air. Earth’s atmosphere did not always have oxygen. The addition of oxygen occurred slowly from about 3.5 billion years ago to about 2.5 billion years ago. Once respiration was able to take place, accelerated oxygen buildup in the atmosphere occurred. Once there was enough oxygen to form a protective ozone layer, other forms of life were able to thrive on Earth.
Atomic Symbol: O
Atomic Number: 8
Discovery: In the late 1700s, three people dedicated time to finding the element in air that promoted combustion.
- Joseph Priestly
- Antoine Levoisier
- Carl Wilhelm Scheele
In Pollution: While oxygen is absolutely necessary for life, it is also harmful to life in the wrong forms. Oxygen is one of the primary components of smog.
Atomic mass, atomic number, electron configuration and other detailed information on the chemistry of oxygen is also available from the Chemistry Guide.
Sources:
NOAA Jetstream: Atmospheric Composition
Windows to the Universe
The Discovery of Oxygen