Oxygen

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Oxygen nuclei contain 8 protons. They were made inside red giant stars and thrown out of them in a supernova.
On the way out they picked up 8 electrons to make oxygen atoms
The shell model explains why oxygen atoms can make 2 covalent bonds. For example when 1 oxygen atom joins with 2 hydrogen atoms they form water molecules as well as many of the molecules of life.
We can think of oxygen atoms as a ball with 2 arms or as a shell with 2 holes.
In models oxygen atoms are usually colored red.
Oxygen atoms like to gain electrons to give themselves a hard outer shell. Oxygen is therefore an oxidizing agent, or electron acceptor.

For the size of oxygen atoms, click here.