7/24/2015
1
Art Ian G. Bautista, ECE, ECT
The type of bond allows us to explain a
material’s properties.
Example: Consider carbon which may exist as
both graphite and diamond. Whereas graphite
is relatively soft and has a ‘‘greasy’’ feel to it,
diamond is the hardest known material. This
dramatic disparity in properties is directly
attributable to a type of interatomic bonding
found in graphite that does not exist in
diamond.
1. Name the two atomic models cited, and note
the differences between them.
2. Describe the important quantum-mechanical
principle that relates to electron energies.
3. (a) Schematically plot attractive, repulsive,
and net energies versus interatomic
separation for two atoms or ions.
(b) Note on this plot the equilibrium
separation and the bonding energy.
4. (a) Briefly describe ionic, covalent, metallic,
hydrogen, and van der Waals bonds.
(b) Note what materials exhibit each of these
bonding types.
Each atom consists of a very small nucleus
composed of protons and neutrons, which is
encircled by moving electrons.
Both electrons and protons are electrically
charged, the charge magnitude being 1.60 x
10-19 C, which is negative in sign for electrons
and positive for protons; neutrons are
electrically neutral.
Protons and neutrons have approximately the
same mass, 1.67 x 10-27 kg,
Each chemical element is characterized by the
number of protons in the nucleus, or the
atomic number (Z).
The atomic mass (A) of a specific atom may
be expressed as the sum of the masses of
protons and neutrons within the nucleus.
Although the number of protons is the same
for all atoms of a given element, the number of
neutrons (N) may be variable. Thus atoms of
some elements have two or more different
atomic masses, which are called isotopes.
