(Metallic, Ionic, Covalent, and van der Waals Bonds)
elementary chemistry it is known that the atomic structure of
any element is made up of a positively charged nucleus surrounded
by electrons revolving around it. An element’s atomic number
indicates the number of positively charged protons in the nucleus.
The atomic weight of an atom indicates how many protons and neutrons
in the nucleus. To determine the number of neutrons in an atom,
the atomic number is simply subtracted from the atomic weight.
Atoms like to have a balanced electrical charge. Therefore, they
usually have negatively charged electrons surrounding the nucleus
in numbers equal to the number of protons. It is also known that
electrons are present with different energies and it is convenient
to consider these electrons surrounding the nucleus in energy
“shells.” For example, magnesium, with an atomic number
of 12, has two electrons in the inner shell, eight in the second
shell and two in the outer shell.
All chemical bonds involve electrons. Atoms will stay close together
if they have a shared interest in one or more electrons. Atoms
are at their most stable when they have no partially-filled electron
shells. If an atom has only a few electrons in a shell, it will
tend to lose them to empty the shell. These elements are metals.
When metal atoms bond, a metallic bond occurs. When an atom has
a nearly full electron shell, it will try to find electrons from
another atom so that it can fill its outer shell. These elements
are usually described as nonmetals. The bond between two nonmetal
atoms is usually a covalent bond. Where metal and nonmetal atom
come together an ionic bond occurs. There are also other, less
common, types of bond but the details are beyond the scope of
this material. On the next few pages, the Metallic, Covalent and
Ionic bonds will be covered in more detail.