Week 1 Flashcards
What defines material properties?
Structure, ‘arrangement of internal components’
can be subatomic, atomic, nanostructure, microstructure or macrostructure
What is atomic mass?
Sum of masses protons and neutrons within the nucleus
What is are Isotopes?
Atoms with two or more difference atomic masses
What is atomic weight?
Weighted average of atomic masses of the atom’s naturally occurring isotopes
How do we calculate average atomic weight?
Average atomic weight = sum of [fraction of occurrence multiplied by atomic weight of isotope]
Definition of Quantum mechanics
Laws/principles governing atomic and subatomic entities
What is the Wave-Mechanical Model
Electron considered to exhibit both wave and particle-like characteristics
How does the Wave-Mechanical Model define position?
not perceived as a particle moving a discrete orbital but but by probability distribution/electron cloud (electron at various locations around the nucleus)
What are the four quantum numbers and their symbols?
Principle Quantum Size/Primary Number - n Shape/Secondary Quantum Number - l (n-1) Orientation - ml (-l to +l) Spin - ms (+1/2 or -1/2)
What are the letter designations for the values of l
0 - s 1 - p 2 - d 3 - f 4 - g 5 - h
What is the ground state?
When all electrons in atom occupy lowest possible energies
What is electron configuration?
(structure of an atom) manner in which these states are occupied
i.e Oxygen(O)
1s2 2s2 2p4
What is the Pauli Exclusion Principle?
No electron state can hold more than two electrons that must have opposite spins
What is Electron State?
Values of energy that are permitted electrons
Trend for electronegativity
Increases going to the right and up(Highest EN - F 4.0)
Decreases going to the left and down(Lowest EN - Fr/Cs 0.7)
What is a property?
Trait in terms of kind and magnitude of reaction to an imposed stimulus.
What are the 6 property classifications?
1) Mechanical
2) Electrical
3) Thermal
4) Magnetic
5) Optical
6) Deteriorative
Mechanical properties?
Applied load; strength, stiffness, resistance to fracture, elasticity.
Electrical properties?
Applied electric field; conductivity; dielectric constant.
Thermal properties?
Temperature change, expansion, heat capacity.
Magnetic properties?
Applied magnetic field, susceptibility, magnetization.
Optical properties?
Electromagnetic radiation, reflectivity, refraction, absorption.
Deteriorative properties?
Chemical reactivity, corrosion, electrode potential.
What defines properties?
Structure; arrangement of internal components.
Subatomic scale?
Electrons within atoms; energies and interactions with nuclei.
What’s the atomic level?
Organization of atom to form molecules or crystals.
Nanostructure level?
Atom aggregates < ~100nm (nanoparticles).
Microstructure level?
Structural elements viewed under microscope.
100nm < size < 1 + mm
Macrostructure level?
Structural elements viewed by naked eye
1+mm < size < 1+ meter
What’s the modified paradigm?
Processing —> Structure —> Properties —> Performance —> Reuse/Recyclability
What’s the Classic Paradigm?
Processing —> Structure —> Structure —> Properties —> Performance
What are the 3 primary Solid Materials?
Metals, ceramics, polymers (Based in chemical makeup and atomic structure)
What’s a metal material?
Mainly metallic elements (nonmetallic in relatively small amounts); atoms arranged in orderly manner
What’s a ceramic material?
Compound between metallic and non-metallic (most frequently oxides,nitrides and carbides); Tetrahedral like structures.
Ceramic vs glass?
Ceramic crystalline vs Glass non- crystalline
What are Polymer materials?
Organic compounds chemically based on carbon, hydrogen, and other nonmetallic elements (O, N, Si); large molecular structures chain-like with carbon atom backbone.
What are the the different properties of metals, ceramics, and polymers?
Add pic later (lec 1, slide 29)
What’s a composite?
Composed of 2 or more individual materials to achieve combination of properties not displayed by any single material; best characteristics of each.
What’s a semiconductor?
Intermediate electrical properties (b/w metals and ceramics/polymers).
Sensitive to presence of tiny concentrations of impure atoms.
Change silicon behaviour by mixing a small amount of impurity (doping)
Work due to imbalance of electrons
Biomaterials?
Used to fix defects, repair or replace defective organ in body.
Inert materials implanted into body to function in a safe, reliable and physiologically safe manner.
Biocompatible; not toxic; desired properties
What are the 4 advanced Materials?
Semiconductors, bio materials, nano materials and smart materials
Smart materials?
Have the ability to sense changed in environment and respond in predetermined manners.
Nano materials?
Distinguished based in size.
Bottom-up approach as opposed to top-down approach- scanning probe microscopes.
What is atomic mass unit?
Amu (unit used to compute atomic weight).
Mass of an electron?
9.11 x 10^-31 kg
Mass of proton/neutron?
1.67 x 10^-27 Kg
Avogadro’s number?
6.022 x 10^23
Magnitude of charge of electron/proton?
1.602 x 10^-19 C
What did the Bohr Model explain?
Position of electron orbitals and quantized energy levels.
What is unique about particle position?
Position is not perceived as particle moving in discrete orbital but by probability distribution/electron cloud (electrons at various locations around the nucleus).
How many electrons are in a S-orbital?
S-orbital is spherical with 2 electrons.
How many electrons in Pi-orbital?
6 electrons in 3 subshells with 2 electrons in each.
What is interatomic bonding
how to atoms interact when they are brought close together from an infinite separation
Attracted - Fa > Fr
Repelled - Fa < Fr
Equilibrium Fa = Fr
What does Fa depend on
Depends on the type of bonding between the atoms
What causes Fr
Due to electron cloud surrounding atom at small r values
When is the net force of fa and fr = 0
at ro (r knot)
At approximately 0.3nm.
Force-energy relationship for two atoms
E = integral of F dr
E net = Ea + Er
Other way around:
F = dE/dr
Types of bonds
Primary:
- Ionic
- Covalent
- Metallic
Secondary/Van Der Waals
What is ground state?
When all electrons in atom occupy lowest possible energies (most stable)
What’s a valence electron?
Those that occupy the outermost shell( can be transferred or shared with another atom).. if filled, configuration is stable.
Aka all electrons outside of nearest inert gas.
Conditions for attraction?
FA > FR
Conditions for repulsion?
FA < FR
What are the conditions for equilibrium?
FA = FR
What is r?
Separation between 2 atoms.
When is force negligible?
As r approaches infinity.
What is E0(Energy knot)?
Bonding energy. Aka minimum require energy to separate 2 atoms to an infinite separation.
Is ionic bonding directional?
No it is non-directional
What does Non-directional mean?
Magnitude of bond is same in all directions.
What’s an ionic bond?
Metal + Non-metal.
Transfer of valence electron.
What’s valency?
Combining capacity of an atom to share/transfer electrons.
How many valence electrons are in Fe? [Ar]3d^6 4s^2
8 electrons (outside of [Ar])
Ionic bonding attractive energy equation?
EA = -A/r
A = (Z1)(Z2)(e^2)/4(pi)(€0)
Z is absolute # valences
€0 is 8.85x10^-12 F/m
e = 1.602 x 10^-19 C
Ionic bonding Repulsive energy equation?
ER = B/r^n
What does directional mean?
Exists only in one direction-b/w atoms sharing electrons.
Is covalent bonding directional?
Yes due to differences in electronegativites of bonded electrons
What’s covalent bonding(hybridization)?
Overlapping of 2 or more orbitals.
Ex sp2 and sp3
What is metallic bonding?
Metals and their alloys, valence electrons not bound to any particular atom, sea of electrons/electron cloud (keeps structure in equilibrium).
Is there any atom bonding in metallic bonding?
No, sea of electrons keep atoms together
Is metallic bonding directional?
No, electron act like glue
Is primary or secondary bonds stronger?
Primary bonds are stronger as they are physical bonds.
What’s a secondary bond?
Bond that exists between all molecules (presence masked by primary bonds), experience by stable electron configuration atoms, arises from atomic/molecular electric dipoles.
What causes secondary interatomic bonding?
Dipole
What’s a dipole?
Separation of positive and negative within the same atom/molecule
Van Der Waals exists between two such molecules
The 3 dipole interactions?
1) Between induced dipoles(temporary/fluctuating)
3) Between induced dipoles and polar molecules
3) Between polar molecules(permanent)
What’s a polar molecule?
Molecule with permanent dipole.
What’s the percent Ionic Character equation?
%IC = {1-exp[-(0.25(XA-XB)^2]} x 100
XA = electronegativity for A XB = electronegativity for B
