Atomic Structure and Energy Levels Quiz

Atomic Structure

• 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.

Energy Levels & Energy Bands

• 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.

Energy Bands

• 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.

Classification of Solids

• 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.

Band Diagram

• A band diagram visually represents the energy bands and their relationships in a solid material.