You're breathing right now and your body is taking in oxygen (O) molecules. You need oxygen to survive, as do almost all other living organisms. It's a good thing that oxygen makes up over twenty percent of the Earth's atmosphere. We are the only planet in the solar system with enough oxygen gas available to let us survive.
Did you know that if you breathe too much oxygen you could die? What about this: If you have a room filled with oxygen and hydrogen (H) and someone lights a match... it will explode! That's because oxygen is very reactive.
Oxygen is the eighth element of the periodic table and can be found in the second row (period). Alone, oxygen is a colorless and odorless molecule that is a gas at room temperature. Oxygen molecules are not the only form of oxygen in the atmosphere; you will also find oxygen as ozone (O3) and carbon dioxide (CO2). A chemist named Priestly isolated oxygen in 1774.
Where else can you find oxygen?
Ozone Layer
In the past couple of years you may have heard of something called ozone. It is a compound that floats in the atmosphere around the Earth. Did you know that ozone is made up of oxygen? That's right. Three oxygen atoms can combine and make ozone.
Plastics
Oxygen is inside things made out of plastic. Every time you get a 2-liter bottle or a yogurt, look at the plastic. Now you know there is oxygen inside all plastics.
Breathable Air
Oxygen is very important. Life on Earth could not exist without it. Animals need to breathe oxygen to survive. Luckily, there is enough oxygen in the air for everyone to breathe.
Rocks and Soils
You just read that there is oxygen in the air. Here's something else... 50% of the Earth's crust is made up of oxygen. That means that no matter what you pick up or dig up from the ground... There's a good chance that one half of it is made up of oxygen.
Water
Over half of the Earth is covered with water. Mixed in that water is oxygen. In the same way we breathe the oxygen in the air, fish breathe the oxygen in the water.