Conductors: Atoms of a group of elements
called metals are held together by a form of bonding. The type of metal we are
concerned with here have single valence electron. For example, copper atom has
29 electrons in orbit round each nucleus. After the first three shells are
filled (2+ 8 + 18 = 28), there is one lone electron in the fourth shell. Since copper atom would have been more stable
without this valence electron, only a very week attraction hold it in orbit
round the nucleus (unlike the 28 tightly bound electrons which fill the first
three shells). As a result, the valence electron often finds itself midway
between the nuclei of any two adjacent copper atoms.
called metals are held together by a form of bonding. The type of metal we are
concerned with here have single valence electron. For example, copper atom has
29 electrons in orbit round each nucleus. After the first three shells are
filled (2+ 8 + 18 = 28), there is one lone electron in the fourth shell. Since copper atom would have been more stable
without this valence electron, only a very week attraction hold it in orbit
round the nucleus (unlike the 28 tightly bound electrons which fill the first
three shells). As a result, the valence electron often finds itself midway
between the nuclei of any two adjacent copper atoms.
In this
position of balanced attraction, the valence electron is then fee to leave its
parent nucleus and to move into the fourth shell of a neighboring atom. The
copper atoms donate their valence electrons to form a vast cloud of free
electrons, thus becoming stable positive copper ions with their 28 tightly
bound orbital electrons. Since the positive metal ions repel one another, they
will take up fixed geometric positions within the electron cloud, thus giving
the metal object its shape. The atoms are held together by the attraction
between the positive metal ions and the common cloud of free electrons.
position of balanced attraction, the valence electron is then fee to leave its
parent nucleus and to move into the fourth shell of a neighboring atom. The
copper atoms donate their valence electrons to form a vast cloud of free
electrons, thus becoming stable positive copper ions with their 28 tightly
bound orbital electrons. Since the positive metal ions repel one another, they
will take up fixed geometric positions within the electron cloud, thus giving
the metal object its shape. The atoms are held together by the attraction
between the positive metal ions and the common cloud of free electrons.
This is
referred to as metallic bonding. Free electrons move through the lattice of
positive metal ion in the seemingly solid copper conductor. This flow of free
electrons in an electric conductor represents an electric current.
referred to as metallic bonding. Free electrons move through the lattice of
positive metal ion in the seemingly solid copper conductor. This flow of free
electrons in an electric conductor represents an electric current.
Insulators: Are materials that have lust the opposite effect on
the flow of electrons as conductors. They do not let electrons to flow very
easily from one atom to another. Insulators are materials whose atoms have
tightly bound electrons. These electrons are not free to roam around and be
shared by neighboring atoms. Some common examples of insulators are glass,
plastic, rubber, air and wood. Insulators are used to protect us from dangerous effects of electricity flowing through conductors. The rubbery coating on
wires is an insulating material that shields us from the conductor inside.
the flow of electrons as conductors. They do not let electrons to flow very
easily from one atom to another. Insulators are materials whose atoms have
tightly bound electrons. These electrons are not free to roam around and be
shared by neighboring atoms. Some common examples of insulators are glass,
plastic, rubber, air and wood. Insulators are used to protect us from dangerous effects of electricity flowing through conductors. The rubbery coating on
wires is an insulating material that shields us from the conductor inside.
Semi conductors: Are materials that exhibit properties that are between a metal and a
non – metal. Their electrical properties are part way between a conductor and
an insulator – thus they are called “semi – conductors” (Actually they are much
closer to insulators than conductors). A major difference between
semiconductors and conductors is their electrical behavior at different
temperatures. In general, when you heat up a semi conductor its resistance to
the flow of electricity decreases (or its conductance increases). In metals the
opposite happens. As the temperature of a metal increases, its resistance also
increases (or conductance decreases).
non – metal. Their electrical properties are part way between a conductor and
an insulator – thus they are called “semi – conductors” (Actually they are much
closer to insulators than conductors). A major difference between
semiconductors and conductors is their electrical behavior at different
temperatures. In general, when you heat up a semi conductor its resistance to
the flow of electricity decreases (or its conductance increases). In metals the
opposite happens. As the temperature of a metal increases, its resistance also
increases (or conductance decreases).
Today silicon is the most commonly used
semiconductor although germanium was used almost exclusively in early (1950’s)
solid state devices.
semiconductor although germanium was used almost exclusively in early (1950’s)
solid state devices.
