reading this section you will be able to do
explanation of the valence shell of an atom.
what free electrons are and why they are important.
is the valence shell?
Notice that in the copper atom pictured
below that the outside shell has only one electron. This represents
that the copper atom has one electron that is near the outer portion
of the atom. The outer shell of any atom is called the valence
shell. When the valence electron in any atom gains sufficient
energy from some outside force, it can break away from the parent
atom and become what is called a free electron.
Pictured here is
an atom of copper, which is much more complex than either an atom
of hydrogen or helium.
Atoms with few electrons
in their valence shell tend to have more free electrons since
these valence electrons are more loosely bound to the nucleus.
In some materials like copper, the electrons are so loosely held
by the atom and so close to the neighboring atoms that it is difficult
to determine which electron belongs to which atom. Under these
conditions, the valence or free electrons tend to drift randomly
from one atom to its neighboring atoms. Under normal conditions
the movement of the electrons is truly random, meaning they are
moving in all directions by the same amount. However, if some
outside force acts upon the material, this flow of electrons can
be directed through materials and this flow is called electrical
current. Materials that have free electrons and allow electrical
current to flow easily are called conductors. Many materials
do not have any free electrons. Because of this fact, they do
not tend to share their electrons very easily and do not make
good conductors of electrical currents. These materials are called
insulators. There will be more information on this later.
shell is the outer shell of the atom.
have a free electron in their valence shell and this electron
can easily move from atom to atom.
electrons are responsible for electrical current.