atom which was created shortly after the big bang.
Hydrogen atoms can join with other atoms using covalent bonds to create hydrogen molecules, water molecules as well as most of the molecules of life.
The shell model of the atom explains why hydrogen atoms can make 1 covalent bond. In ball-and-stick diagrams we show hydrogen as a ball with one stick. In space filling models we show hydrogen as a ball with one hole.
In models hydrogen atoms are usually colored white. In the pictures in this journal they are a pale green color.
For the size of hydrogen atoms, click here.