1. Conductors are materials that allow the flow of electric charges through them. Most metals are good conductors due to their crystalline structure and delocalized electrons. 2. In metallic solids, the atomic orbitals overlap to form energy bands. In conductors, the valence band is partially filled or overlaps with the empty conduction band, allowing electrons to move freely through the material. 3. Common good conductors include copper, silver, and gold. Conductivity decreases with increasing temperature as atomic vibrations interfere with electron flow. 4. Some materials become superconductors below a critical temperature, allowing infinite conductivity and perfect diamagnetism due to the Meissner effect. This occurs due to

1. Conductors
Al-Azhar University of Gaza
Faculty of Science
Chemistry Department
Preparation by:
Mohammed H. Rida
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2. Solid materials are classified into:
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3. Definition of conductors
a conductor is an object or type of
material that permits the flow of electric
charges in one or more directions
,commonly metal.
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4. 4

5. Metallic crystals
• Except for the actinides, most metals crystallize in
• A- simple cubic packing
• B- hexagonal close-packed (hcp)
• C- and cubic close packed (ccp)
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6. Properties of metals
 Metals have high conductivity, or low resistance, to the passage
of electricity and heat.
 nonmetals have low conductivity or high resistance.
 most can be shaped by hammering or bending.
 This is possible because the bonding is non directional.
 each atom is rather weakly bonded to all neighboring atoms,
rather than to individual atoms, as is the case in discrete
molecules.
 When force is applied, the atoms can slide over each other and
realign into new structures with nearly the same overall energy.
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7. Metallic Solids
• Metals are excellent conductors of both heat and electricity and
this is not a coincidence.
* A metal is a good conductor of electricity because there are a large
number of free electrons (the valence electrons).
* A small electric field across the metal causes the negative electrons
to migrate to the positive side and this produces an electrical current.
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8. MOLECULAR ORBITALS AND BAND theory
When molecular orbitals are formed from two atoms,
each type of atomic orbital gives rise to two molecular
orbitals.
 When n atoms are used, the same approach results in n
molecular orbitals.
 Because the number of atoms is large, the number of
orbitals and energy levels with closely spaced energies is
also large.
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9. The result is a band of orbitals of similar energy, rather
than the discrete energy levels of small molecule.
 These bands then contain the electrons from the atoms.
 The highest energy band containing electrons is called the
valence band;
 the next higher empty band is called the conduction band
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10. 10

11. In conductors, the valence band is either not
fully occupied with electrons, or the filled
valence band overlaps with the empty
conduction band.
In general, both states occurs at the same time,
there is free movement of electron ,the
electrons can therefore move inside the
partially filled valence band or inside the two
overlapping bands.
In conductors there is no band gap between
the valence band and conduction band.
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12. The conduction in metals arises from:
(a) the delocalization of the electron energy levels over the entire solid.
(b) the availability of empty orbitals in a given band permitting
movement of the electrons.
* Almost no energy is required to promote the electrons to the open
level.
* In fact the energy separation of the constituent s and p orbitals are
close enough that for the solid the s and p bands overlap.
The highest occupied level in the band is known as the Fermi Level.
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13. In fact the energy separation of the constituent s and p
orbitals are close enough that for the solid the s and p
bands overlap.
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14. Common conductors:
• Most familiar conductors are metals
 Cu is the most common material used for electrical wiring
 Ag is the best conductor but its expensive ,
 Au is used for high quality surface to surface contact because it
doesn’t Corrode .
 There is Some non-metallic conductors like graphite ,solution of salt
And some polymer.
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15.  The conductance of metals decreases with
increasing temperature,
 because the increasing vibrational motion of
the atoms interferes with the motion of the
electrons and increases the resistance to
electron flow.
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16. Superconductors.
exhibits no resistance to electrical conductivity, & will oppose an external
magnetic field, a phenomenon referred to as the Meissner effect
Photograph of the Meissner effect for a rare-earth magnet above a sample of
YBCO (YBa2Cu3O7)immersed in liquid nitrogen. The onset of strong
diamagnetism (“superdiamagnetism,” as observed by the repulsion of an
external magnetic field) is the most reliable method to determine
superconductive behavior.
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17. SUPER CONDUCTlVlTY
The conductivity of some metals changes abruptly near liquid helium
temperatures (frequently below 10 K), and they become
superconductors,
 In this state, the metals offer no resistance (zero resistance) to the
flow of electrons, and currents started in a loop will continue to
flow indefinitely (several decades at least) without significant
change.
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18. *For chemists, one of the most uses of this effect is in
superconducting magnets used in nuclear magnetic resonance
instrument in which they allow generation of much larger magnetic
fields than can be obtained with ordinary electromagnets.
*A major goal of superconductor research is a material that is
superconducting at higher temperatures, to remove the need for
liquid helium and liquid nitrogen for cooling.
*a year later, first material with a critical point above boiling point
of nitrogen (77 K) was discovered, known as:
- YBa2Cu3O7, with a critical point of 92K
- Hg0.8Tl0.2Ba2Ca2Cu3O8.33, Tc = 138 K 18

19. Resistivity ρ
(Ω·m)
Material
0Superconductors
10−8Metals
variableSemiconductors
variableElectrolytes
1016Insulators
relative to the conductivity of pure water at 25 °C. An EC meter is
normally used to measure conductivity in a solution. A rough summary
is as follows:
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