Atomic Structure and Energy Levels Quiz

Study Notes

Atoms are composed of a positively charged nucleus surrounded by electrons in specific orbits.
Each orbit has a maximum electron capacity of 2n², where 'n' represents the orbit number.
Electrons move to higher energy orbits when they absorb energy, and they emit light or heat when they fall back to lower orbits.

The fixed energy possessed by electrons in an orbit of an isolated atom is called an energy level.
The range of energies possessed by electrons in an orbit within a solid material is known as an energy band.

The valence energy band (V.B) encompasses the energy range of valence electrons.
The conduction energy band (C.B) represents the energy range of free or conduction electrons.
The forbidden energy band gap (Eg) separates the conduction and valence bands.

Insulators: Materials that resist the flow of electric current.
Example: Glass, wood, paper.
In insulators, the valence band is full, and the conduction band is empty.
Their energy gap is very large, typically around 15 eV.
Conductors: Materials that readily allow the flow of electric current.
Example: Copper, gold.
Conductors have a large number of free electrons in the conduction band.
Their conduction and valence bands overlap.
A small potential difference causes electron flow, leading to current.
Conductors exhibit a positive temperature coefficient of resistance.
Semiconductors: Materials with conductivity between that of insulators and conductors.
Example: Silicon, Germanium, GaAs, GaP.
They have a small energy gap between the conduction and valence bands.
Electrons can easily move from the valence band to the conduction band with minimal energy input.
Semiconductors show a negative temperature coefficient of resistance.