Valence electrons are the electrons that are on the outermost shell of the atom’s electrons which are can be either given away, added, or to be shared. When these electrons are given away, added to or shared, there is a chemical change occurring and the compound that is formed is changed from the original elements. This is called bonding which is pretty much the realm of the electrons. It is the sharing of electrons from each atom that define the chemical bond.
Because all bonds involve the sharing of electrons, we can say that all bonds are covalent. It’s just that some are more polar that others and some are very, very polar. It is the latter which take on some of the characteristics of an ionic bond. The ionic and covalent bonds are known to be the strongest chemical bonds. An ionic bond forms when two atoms differ so much in electronegativity that one or more electrons are actually transferred from one atom to the other. Ionic bonds generally occur between a metal and a nonmetal.
Due to the existence of ionic bonds, elements that normally would not combine because sharing electrons is either not possible or not practical may be combined to form chemical compounds. A covalent bond forms when two atoms share a pair of electrons. The sharing of one pair of electrons produces a single bond whist the sharing of two or three pairs of electrons produces double or triple bonds. If both atoms are equally electronegative, a nonpolar covalent bond forms.
If one atom is slightly more electronegative, a polar covalent bond formulates. Covalent bonds allow the greatest possible combinations of chemical compounds to take place. Here is an example of chemical bonding of H 20: H-O-H. This tells us that the formula of H20 is one molecule of water which is made of two atoms of hydrogen and one atom of oxygen bonded together. The bonds which hold the hydrogen and oxygen together are called covalent bonds which are very strong.