Atoms, Electrons, and Energy Levels
What matter is made of
Atoms and electrons
All materials are made of atoms. Atoms have a nucleus and electrons around it. Electrons do not move in arbitrary amounts of energy; instead, they occupy allowed energy levels. This idea is essential for understanding why some materials conduct electricity and others do not.
Valence and bonding
The outermost electrons of an atom are called valence electrons. In solids like silicon, atoms share valence electrons in covalent bonds. These bonds create a stable crystal structure.
Core idea
A semiconductor’s electrical behavior depends strongly on how tightly its electrons are bound and how easily they can move.
Important vocabulary
What are valence electrons?
Valence electrons are the outermost electrons and are important in chemical bonding.
Correct answer: Outer electrons involved in bonding
What is a covalent bond?
In covalent bonding, atoms share electrons to become more stable.
Correct answer: a bond formed by sharing electrons
Free electrons vs bound electrons
Free electrons
- Can move through the material more easily
- Help carry electric current
Bound electrons
- Held tightly in bonds or atoms
- Do not contribute much to current
Why do electrons matter so much in semiconductor science?
Electrical conduction is mainly about how electrons behave in the material.
Correct answer: They determine how electricity moves through the material.