Learning Module A6 Flashcards
What is the relationship between the conductivity of materials and their atomic structure?
The conductivity of a substance depends closely on its valence electrons.
What are the characteristics of the best electrical conductors?
Atoms that have three or fewer valence electrons.
Why can outermost electrons in good conductors easily become free electrons?
They are loosely held in orbit.
Give an example of a good electrical conductor and its valence electrons.
Aluminum has three valence electrons; copper has one valence electron.
What defines insulating materials in terms of valence electrons?
Insulating materials have five or more valence electrons.
What is the ideal number of electrons in the valence orbit for an insulator?
Eight electrons.
Why are valence electrons in insulating materials not easily given up for current flow?
They tend to be held more tightly in orbit.
What type of materials are semiconductors considered to be?
Neither good conductors nor good insulators.
How many valence electrons do semiconductor elements have?
Exactly four valence electrons.
Name two commonly used semiconductor elements.
Silicon and germanium.
Which semiconductor is more popular and why?
Silicon, because of its ability to withstand higher temperatures.
Fill in the blank: The best electrical conductors have _______ valence electrons.
three or fewer valence electrons.
Fill in the blank: The ideal insulator contains _______ electrons in its valence orbit.
eight.
True or False: Semiconductors have a higher conductivity than good conductors.
False.
What is the unique arrangement of atoms in purified semiconductor materials called?
Crystal-lattice structure
This structure is essential for the properties of semiconductors.
What process involves atoms sharing their valence electrons to create a stable arrangement?
Covalent bonding
This leads to a stable eight-electron arrangement.
What is the term for introducing a small amount of impurity into a semiconductor?
Doping
Doping improves the conductivity of semiconductors.
What are the two distinct types of semiconductor material produced by doping?
N-type and P-type
The type depends on the impurity used.
What type of semiconductor is formed when an impurity with five valence electrons is introduced?
N-type semiconductor
This involves pentavalent impurities.
Name three pentavalent elements that can be used to dope semiconductors.
- Arsenic
- Antimony
- Phosphorous
These elements contribute free electrons to the semiconductor.
What happens to four of the five valence electrons of a pentavalent impurity atom?
They form covalent bonds with adjoining semiconductor atoms
This bonding is crucial for semiconductor structure.
True or False: In an N-type semiconductor, one electron from the pentavalent impurity is free to move through the crystal.
True
This free electron contributes to electrical conductivity.
What type of semiconductor material is referred to as N-type?
A semiconductor material with a surplus of electrons, or negative charge carriers, within the covalent structure
N-type semiconductors are created through doping with donor atoms that provide extra electrons.
What effect does doping have on the conductivity of N-type semiconductors?
It greatly improves the conductivity due to the free electrons developed by the doping process
The presence of free electrons allows for easier flow of current.
