FREE ELECTRON IN METALS I
Component
structure atom
semiconductor(silicon)
insulators(wood)
comparison
insulators; do not allow electric current to flow through them
semiconductors; Materials whose conductivity lies in between of conductors and semiconductor
conductors; Allow electric current to the flow through them
basic units of matter
defining the structure of elements
made up of three particles protons, neutrons n electrons
protons n neutrons heavier>electrons
center of atom=nucleus
INTRODUCTION
have a high resitance so current does not flow in them
conductivity between 10^-8 o <10^4 S m^-1
conductors(metals)
has four electron in its outer or valence orbit
can be conditioned to act as good conductors, or good insulators
conductivity between 10^10<0<10^4 S m^-1
element=copper,silver,goid alloys=brass,steel liquid=salt water
have low resistance so electrons flow through them with ease
only one electron in their oiuter shell.
its called a valence electron
not strongly bonded to the nucleus
conductivity between 10^-16<o<10^-8 s m^-1
glass,ceramic,plastics and wood
most are compounds of several elements
the atoms are tightly bound to one another
a metal can be considered to consist of ion cores having the nucleus and electrons other than valence electrons
form an electron gas surround the ion cores and are free to move anywhere within the metals
electron theory
stage 1:.:- The Classical Free Electron Theory
Stage 2:- The Quantum Free Electron Theory
Stage 3:- The Band Theory or Zone Theory
Classical Free Electron Theory of Metals
was developed by Drude and Lorentz during 1900, known as Drude-Lorentz theory
In metals, there are a large number of free electrons moving freely within the metals. The electrons revolve around the nucleus in an atom
Electric conduction is due to motion of free electrons only. The +ve ion cores are at the fixed positions. The free electrons undergo incessant collisions with the ion core
When an electric field is applied to the metals, the free electrons are accelerated in the direction opposite to the direction of applied electric field
The Free Electron Model
that conduction electrons exist & that they consist of the valence electrons from the metal atom
Electron gas model in metals
DRUDE MODEL
Success of classical free electron
theory
It verifies Ohm’s Law.
It explains the electrical and thermal conductivities of metals.
It derives Wiedemann – Franz Law (i.e., The relation between electrical and thermal conductivities).