Conduction by Metals: Why do Metals Conduct electricity?

Metals have a sea of free electrons in their structures. These electrons are the source of conduction when in an electric circuit. Electric current is defined as the passage of electrons through a substance.

Metals are closely packed materials having lattice structures called metallic lattices. Every atom in a metallic lattice is surrounded by a sea of electrons. When electrons from the electric source (battery) come along, lattice electrons are pushed out. Metals continue to do so (conduct electricity) until the lattice electrons are being replaced, not removed.

Chemical bonding

The atoms of the elements are bonded together by ionic, covalent, and coordinate (dative) covalent bonds. Another type of bond, the metallic bond, is present between metals only.

Metallic bonds

The electrostatic force of attraction between positively charged atoms and a sea of electrons is termed metallic bonds. The greater the number of electrons in the sea, the greater would the ability of metals to conduct electricity.

  • Metals are closely packed substances, showing the strength of metallic bonds.
  • Atoms are arranged as layers.
  • The transition metals have a very high tensile strain, as a property of metallic lattices.
  • Metals are malleable and ductile.

Free electrons

The electrons present in lattices of materials are called free electrons. The word ‘free’ refers to, ‘being unbound’. The electrons are free of the atomic boundaries but they are bonded to the surrounding atoms by attractive forces called the metallic bond.

Free electrons, being free to move in row formations, as long as they are being replaced, ‘not removed’ are the reason for electrical conductance among metals.

Why do metals conduct electricity?
Structure of metallic lattice and free electrons

Current Electricity

Electric current is the movement of electrons from a substance. The flow of current is due to a potential difference created at both ends of a substance. Ohm’s law states that;

The applied current is directly proportional to an applied voltage.

V ∝ I

V = I.R

‘R’ is the proportionality constant called resistance.

Resistance (R) is the ability of materials to resist the flow of electricity through them. It is the loss of electrons from the battery source. Some electrons enter a substance through one side but never leave the other one, meaning that the reduction in the number of electrical charges during conduction is termed resistance.

The resistance of a substance depends on the following parameters.

  1. Length of the wire or metal piece, the subject of conduction.
  2. The width of the wire provided that, electrons are driven perpendicularly to the width.
  3. The cross-sectional area of metallic substance, conducting electrons (1+2).
  4. The nature of conducting materials.

Conduction band theory (CBT)

According to conduction band theory, the valence and conduction bands in metals are very close to each other. It looks like they overlap one another. When metals are connected to a source (battery), electrons of the valence band may jump into the conduction band, easily. These electrons and this jumping are responsible for the conduction property of metals.

Conduction band theory, Why do metals conduct electricity?

Types of electric conductors

There are three types of electric conductors:

  1. Conductors
  2. Semiconductors
  3. Insulators

According to CBT (Conduction Band Theory), metals are conductors with an overlap between conduction and valence bands. Semi-conductors are intermediates with a small difference between valence and conduction bands. Insulators have a large difference between valence and conduction band which becomes the reason why, insulators cannot promote their electrons to the conduction band in order to become conductors.

Electric Conductivity

Electric conductivity is the reciprocal of the Resistivity of a substance. Resistivity is the ‘retardation per unit length’ of electron flow in a circuit.

R = rowL/A, The equation of resistance and resistivity

where,

  • R = Resistance
  • ρ = resistivity
  • L = length of conduction region in a wire
  • A = Cross-sectional area of a metal

Effect of temperature of electric conductivity

By increasing the temperature, the vibrations of atoms increase. These vibrations lead to a large number of increased collisions due to which, the availability of free electrons is diminished. Hence, conductivity decreases by increasing the temperature.

Alloys and Their conductivity

When different metals are fused together, a solid-solid solution is formed, called an alloy. Usually, metals are alloyed to increase their strength. But it may decrease their conductivity.

Related Topics

Concepts Berg

Why are metals good conductors of electricity and heat?

Metals have free electrons, which are the source of current in them. When a potential difference is applied the electrons start flowing in the circuit.

Why do metals conduct heat and electricity so well? What metals conduct the best?

Metals conduct heat and electricity very well in comparison with other solids because of metallic bonds. The positively charged atoms are bonded with a stream or sea of free electrons. Thus, electrons are readily available for conduction. Silver, copper, and gold are the best conductors of electric current in metals.

Why silver metal best conducts electricity?

Pure silver is considered the best conductor of electricity. It shows special behavior due to lanthanide contraction. i.e., as we move along the period of transition elements, the effective nuclear charge increases significantly with the reduced atomic size of the silver atom. Moreover, the unique structure of the silver (Ag) atom makes it the best among other metals. Copper and gold are at 2nd and 3rd place respectively.

Do all metals conduct electricity?

All metals are good conductors of electricity. They are classified into two categories based on their conductivity. For example, copper, gold, and silver are good conductors while sodium, potassium, and magnesium show relatively low conduction. Hence, they are called normal conductors.

What Is copper used for?

Copper is widely used in electric appliances e.g electric motors, generators, connecting cables, etc.

What is electrical conductivity?

Electric conductivity is defined as, the ability of a substance to conduct heat and electric current. It is a reciprocal of resistivity which is the opposition to current flow.

It is denoted by the symbol Rho (Ρ). The unit of conductivity is mho or ohm-1 or siemens per meter.

What type of a conductor, water is? (Ion Conduction)

As pure water has a very little number of ions (10-7 molecules dissociated molecules per mole). It is considered a bad conductor of electricity.

Why do metals conduct electricity and dielectrics do not?

Metals conduct electricity because they have free electrons whereas, dielectrics are insulators. Dielectrics do not have any free species present. They are placed between conducting plates in a capacitor so, only polarization can occur in dielectrics.

Is steel a good conductor?

Steel is not a good conductor. It is an alloy made up of iron, chromium, and carbon. Steel is an interstitial type of alloy. i.e, It is composed of metals with different atomic sizes. They are manufactured to design highly corrosion-resistant and strong structures. e.g doors, stairs, etc.

Why is magnesium a good conductor of electricity?

Magnesium is a good conductor of electricity, but not that good when we compare it with copper. It has metallic bonds in which electrons are delocalized over Mg atoms. These free electrons are responsible for the conduction of current.

Does water conduct electricity?

Water is a weak or poor conductor of electricity.

Why do metals conduct heat?

Metals are in continuous vibratory motion, When one end of it is heated, it travels along with the substance. This phenomenon is known as conduction. The heat is passed over to the next atoms by free electrons.

Do metals conduct electricity when solid?

Yes, metals can conduct electricity even when they are solids. This is due to the availability of delocalized electrons.

Why do metals conduct electricity below zero kelvin?

Metals can conduct electricity even near zero kelvin because at that extremely low-temperatures electrons are still in planetary (supposed) movement.

Why is glass a bad conductor of electricity

Glass is a supercooled liquid substance. SiO2 is arranged to form a lattice through a giant covalent structure. Since no free electrons or ions are present to conduct electricity, glass is not a conductor.

How are ions able to conduct electricity?

Ions can conduct electricity because they are free to move in the solution. Ionic compounds can also conduct electricity due to the mobility of their ions in the molten state.

Why does carbon not conduct electricity?

Carbon has three allotropic forms i.e. diamond, graphite, and buckyballs.

  • Graphite is a layered structure in which carbon sheets are connected through pi electrons. These delocalized electrons are carriers of current.
  • In a diamond, carbon is arranged in a tetrahedral manner throughout the macromolecule. No free electrons are present, so, it is a non-conductor.
  • Similar to diamond, buckyballs are also insulators. There are 40 to 60 carbon atoms joined through covalent bonding. These balls-like structures are connected through induced dipole instantaneous dipole interactions.

Why do ceramics not conduct electricity?

Ceramics are non-metallic materials and non-metals are non-conductors.

References

  • Note on Electrical Conduction in Metals at Low Temperatures, Issue 307 By Francis Briggs Silsbee (American Institute of Physics)

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