Introduction to Covalent Bonding:
Bonding between non-metals consists of two electrons shared
between two atoms. In covalent bonding, the two electrons shared
by the atoms are attracted to the nucleus of both atoms. Neither
atom completely loses or gains electrons as in ionic bonding.
There are two types of covalent bonding:
1. Non-polar bonding with an equal sharing of electrons.
2. Polar bonding with an unequal sharing of electrons. The
number of shared electrons depends on the number of electrons
needed to complete the octet.
Water, the most universal compound on all of the earth, has
the property of being a polar molecule. As a result of this property,
the physical and chemical properties of the compound are fairly
Hydrogen Oxide or water forms a polar covalent molecule. The
graphic on the left shows that oxygen has 6 electrons in the
outer shell. Hydrogen has one electron in its outer energy shell.
Since 8 electrons are needed for an octet, they share the electrons.
However, oxygen gets an unequal share of the two electrons
from both hydrogen atoms. Again, the electrons are still shared
(not transferred as in ionic bonding), the sharing is unequal.
The electrons spends more of the time closer to oxygen. As a
result, the oxygen acquires a "partial" negative charge.
At the same time, since hydrogen loses the electron most - but
not all of the time, it acquires a "partial" charge.
The partial charge is denoted with a small Greek symbol for delta.