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Summary - Fundamentals of Materials Science and Engineering
2 Atomic Structure and Interatomic Bonding
Name the two atomic models cited, and note the differences between them.Bohr and wave mechanical. Whereas the Bohr model assumes electrons to be particles orbiting the nucleus in discrete paths, in wave mechanics we consider them to be wavelike and treat electron position in terms of probability distribution.
Describe the important quantum-mechanical principle that relates to electron energies.The energies of electrons are quantized, only specific values of energy are allowed.
What bonds contain Polymers?Covalent bonds
What are the four quantum numbers?N, l, ml, and ms.
What is the Pauli Exclusion principle?Each electron state can accommodate no more than two electrons which must have opposite spins.
What bonds contain metals?Metallic bonds
What bonds contain ceramics?Ionic bonds/mixed ionic-covalent bonds
What bonds contain molecular solids?Van der Waals bonds
What bonds contain Semi-metals?Mixed covalent-metallic bonds
What bonds contain intermetallics?Mixed metallic-ionic bonds
Properties of solid materials can depend on geometric atomic arrangements and also by interactions that exist among constituent atoms or molecules.
What do properties of solid materials depend on?The geometric arrangements and by interactions that exist among constituent atoms or molecules.
2.2 Fundamental Concepts
Each atom consists of a nucleus composed of protons and neutrons and is encircled by moving electrons. Electrons and protons have an electrical charge of 1.602x10^-19 C. Neutrons are electrically neutral.
What do atoms consist of?A nucleus composed of positively charged protons and neutrally charged neutrons encircled by moving electrons with a negative charge.
The atomic number is equal to the amount of protons in the nucleus.
What is the atomic number equal to?The amount of protons in the nucleus of the atom.
The atomic mass of a specific atom is the sum of the masses of protons and neutrons within the nucleus. The number of neutrons may vary for atoms of the same element, these atoms are called isotopes.
What is the atomic mass of a specific atom?The sum of the masses of protons and neutrons within the nucleus.
What are isotopes?Atoms of the same element with a different amount of neutrons.
The atomic mass unit (amu) may be used to compute atomic weight.
What is amu?The atomic mass unit which can be used to compute atomic weight.
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What is comparison?
The comparing of grain structures with standardized charts, which are based upon grain areas.
What is linear intercept?
A grain-size determination technique that counts numbers of grain boundary intersections by straight test lines.
How does the SPM work?
The microscope generates a topographical map on an atomic scale, that is a representation of surface features and characteristics of the specimen.
What are consequences of the short wavelengths of electron beams?
The high magnifications and resolving powers of these microscopes.
How does an electron microscope work?
An image of the structure under investigation is formed using beams of electrons.
What is a consequence of etching?
Small grooves forming along grain boundaries.
What are the basic elements of optical microscopy?
Optical and illumination systems.
Name three kinds of microscopes
Optical, electron and scanning-probe microscopes
Large enough structural elements to be observed with the unaided eye.
What is a catalyst?
A substance that speeds up the rate of a chemical reaction without participating in the reaction itself.