Here are four different ways chemists use to show a molecule of oxygen. In colored molecule models like these, oxygen is usually red.
Click on image for full size
Windows to the Universe original artwork by Randy Russell.
Oxygen (O2) is a kind of gas. A lot of the air you breathe is oxygen. That's a good thing, since we need oxygen to stay alive!
About 4/5ths of the air in Earth's atmosphere is nitrogen (N2). Almost all of the rest of air is oxygen.
Normal oxygen molecules have two oxygen atoms in them. There is another, less common kind of oxygen. It is called ozone. Ozone molecules (O3) have three oxygen atoms in them.
Many kinds of molecules have oxygen atoms in them. Some of the most important ones are water (H2O), carbon dioxide (CO2), carbon monoxide (CO), sulfur oxides (SO2 and SO3), and nitrogen oxides (NO and NO2).
Most living creatures need oxygen to get energy from food. This is called respiration. That's why we need to breathe oxygen! Plants and some kinds of microbes make oxygen. They use sunlight to make food. That is called photosynthesis. They give off oxygen during photosynthesis.
When Earth was young, its atmosphere didn't have much oxygen. Then microbes and plants started adding oxygen to the air. Now we have quite a bit of oxygen in the air. Lucky for us!
Shop Windows to the Universe Science Store!
Learn about Earth and space science, and have fun while doing it! The games
section of our online store
includes a climate change card game
and the Traveling Nitrogen game
You might also be interested in:
Most things around us are made of groups of atoms connected together into packages called molecules. Molecules are made from atoms of one or more elements. Some molecules are made of only one type of...more
Have you ever heard of ozone? That's a word that shows up in the news a lot! Do you know what ozone is and why it is important in the Earth's atmosphere? Ozone is made of three oxygen atoms (O3). You've...more
Carbon dioxide (CO2) is a kind of gas. There isn't that much carbon dioxide in Earth's atmosphere, but it is still very important. Carbon dioxide is a greenhouse gas. That means it helps trap heat coming...more
Carbon monoxide is kind of gas. It is poisonous. A molecule of carbon monoxide (CO) has one carbon atom and one oxygen atom. Earth's atmosphere has a small amount of carbon monoxide in it. The carbon monoxide...more
You may have heard of photosynthesis. That's where a plant uses energy from the Sun's rays to make its own food. The opposite of photosynthesis is called respiration. The difference is that respiration...more
There are many different kinds of plants. Some have big leaves. Some have small leaves. Some even have flowers. All plants make their own food. When sunlight hits the leaves of a plant, photosynthesis...more
Two scientists have discovered an easy way to get pure oxygen from water using a small amount of electricity. This discovery may become an important new green-energy source. To produce oxygen, they added...more