Answer:
Conductors and Insulators
Conductors
As was shown in Figure 741.1.2, the nucleus of the copper atom
contains 29 protons. A neutral copper atom must therefore have 29
electrons distributed amongst its various shells. Shells k, 1, and m are
filled to capacity with a total of 28 electrons, so there is only one
electron in the n shell. The outermost shell of an atom, the n shell in
this case, is called the valence shell, and the number of electrons it
contains strongly influences the electrical properties of the element
that the atom represents.
figure 741.2.1 Free electron
(click to activate)
Since electrons in the valence shell are the farthest removed from
their nucleus, they experience the least force of attraction to the
nucleus. Coupled with the fact that electrons in a nearly empty shell
are easily dislodged from that shell, we find that the lone electron in
the valence shell of copper can readily vacate that shell. When an
electron breaks away from its ‘parent’ atom, it is called a free
electron, since it is then free to wander randomly through the
material.
An atom producing such a free electron acquires a net positive
charge, because its total number of protons is then one greater than
its total number of electrons. Such an atom is called a positive ion.
To become free, an electron must acquire enough energy to
overcome the force that binds it to its nucleus. In copper, there is
enough heat energy at ordinary room temperatures to liberate a vast
number of the weakly held valence electrons.
Explanation:
