H20
Here is an Oxygen atom.
It has 6 outer electrons, and would be more stable if it had 8.
Here is a Hydrogen atom.
It has one outer electron, and would be more stable if it had 2.
Under the proper circumstances, Oxygen and Hydrogen overlap their electron
clouds, so that each one becomes more stable.
As drawn above, the Hydrogen atom is stable, but the Oxygen could use
one more electron.
A second Hydrogen added in makes all 3 atoms stable.
Notice that all atoms are now more stable because their outer levels are full.
The elcectrons spend their time zipping all over the place with both atoms, not just their original atom.
