Questions and Answers
What happens to an electron when it is given additional energy?
What is the term used to describe the potential required to remove an electron from the outermost shell?
What type of bonding is formed when the valence electrons of one atom form a bonding arrangement with four adjoining atoms?
What is the outermost electron orbital of an atom called?
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What happens when an electron falls back to its original lower orbit?
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What is the term used to describe atoms that have four valence electrons?
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What is the energy level that electrons can jump up into from the valence band when excited?
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What is the state of an atom when an electron is lifted to a higher orbit?
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What is the term used to describe the energy difference between the highest occupied energy state of the valence band and the lowest unoccupied state of the conduction band?
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What is the characteristic of an electron that has left its parent atom?
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What is the term used to describe the separation between any two shells on the energy level diagram?
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What is the characteristic of a conductor?
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What is the characteristic of an insulator?
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What is the characteristic of a semiconductor?
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What is the type of semiconductor that is constructed of two or more materials of different atoms?
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Why do conductors easily allow electric current to flow through them?
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Study Notes
Electron Energy Levels
- Electrons in permitted orbits have a certain amount of energy, with larger orbits having greater energy.
- When an electron gains additional energy, it is lifted to a higher orbit, causing the atom to be in a state of excitation.
- When the electron falls back to its original orbit, it releases energy in the form of heat, light, or other radiations.
Atomic Structure of Si and Ge
- Germanium and silicon have four electrons in their outermost shell, known as valence electrons.
- Atoms with four valence electrons are called tetravalent, with three being trivalent and five being pentavalent.
- The energy required to remove a valence electron from the atomic structure is significantly lower than for any other electron.
Covalent Bonding
- In pure silicon or germanium crystals, the four valence electrons of one atom form a bonding arrangement with four adjoining atoms.
- This sharing of electrons strengthens the bonding between atoms, known as covalent bonding.
Valence and Conduction Bands
- The valence band is the outermost electron orbital that electrons occupy in an atomic structure.
- The conduction band is the band of electron orbitals that electrons can jump into when excited.
- The energy difference between the valence and conduction bands is called the band gap, indicating electrical conductivity.
Energy Levels
- The farther an electron is from the nucleus, the higher its energy state.
- Electrons that have left their parent atom have a higher energy state than those in the atomic structure.
- Within an atomic structure, there are specific energy levels associated with each shell and orbiting electron.
Classification of Solids
- Insulators have a full valence band and an empty conduction band, with a large energy gap (≈ 15 eV).
- Conductors have overlapping valence and conduction bands, allowing easy electric current flow.
- Semiconductors have a valence band that is almost full and a conduction band that is almost empty, with a small energy gap.
- Semiconductors can be classified as single crystal (Si, Ge) or compound crystal (GaAs, GaN, CdS).
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Description
This quiz covers the basics of atomic structure, electron orbits, and excitation states. Learn about the energy levels of electrons and how they transition between orbits.
