Carbon can also form covalent bonds with other atoms of carbon, thus making long, stable chains possible. These are very important to living organisms. The hydrogen protons are equally spaced in three dimensions around the carbon. The shape of a water molecule is also a tetrahedron. 2 O. Oxygen's other four valence electrons, in two pairs, are not bonded to any other atoms, thus these are referred to as unshared pairs of electrons .
Oxygen shares electrons with hydrogen, but pulls just a little harder on the electrons.
The electrons are just a little closer to the oxygen than the hydrogens, so this is called a polar covalent bond . This is called hydrogen bonding . Actually, hydrogen bonding can happen with other molecules besides water as we will see later. Water is a key ingredient in all life. Water has many unique properties due, in great part, to its hydrogen bonding.