The chemical composition of water is
H2O, which means that it contains
two hydrogen atoms and one oxygen atom. Each
one of these atoms has a nucleus and orbitals that
surround the nucleus. An onion is a great example
of an atom since it has many concentric layers.
The very center of the onion represents the
nucleus and the outer layers of the onion
represent the orbitals.
There is a specific number of electrons that
are contained in each orbital, and the total
number of electrons is well known for each element
that we contain in a group of elements called
the periodic table. All elements want to be
stable, and they can do this by having a
completely filled valence orbital (the
valence orbital is the outer most orbital that
Both oxygen and hydrogen do not have completely
filled orbitals and that makes them unstable, so
they want to do something to make themselves
Hydrogen has only one electron in the valence
orbital, but it needs two electrons to be stable.
Oxygen has six electrons in the valence orbital,
but it needs eight to be stable. By sharing
electrons with each other, the two hydrogen atoms
and one oxygen atoms can become stable since they
will all have completely filled valence orbitals.
See picture on this
When electrons are shared between two atoms,
a covalent bond is formed, thus turning oxygen and
hydrogen into water.