MSE 2001 test two (not mine)
A series of similar metal alloys have the following enthalpies of fusion: Alloy A: 4 kJ / molAlloy B: 14 kJ / molAlloy C: 7 kJ/ molAlloy D: 20 kJ / molBased on this information, can you predictively rank these alloys from least stiff to most stiff? (Least Stiff) A < C < B < D (Most Stiff) (Least Stiff) A < B < C < D (Most Stiff) (Least Stiff) D < B < C < A (Most Stiff) It is NOT possible to make a reasonable prediction from the information provided.
(Least Stiff) A < C < B < D (Most Stiff)
The thermal energy of a single atom in a solid at room temperature (25°C) is approximately: 4.1x10-21 eV 0.0022 eV 3.45x10-22 eV 0.026 eV
0.026 eV
Rotational Symmetry plus translation which rotatiuonal symmetries when combined with translation can fill all of the 2d space
1-fold 2-fold 3-fold 4-fold 6-fold not 5 fold 8 fold
rectangle fold symmetry
2
rotoinversion
2 transformation rotation around 360/n immediately followed by an inversion at the center of symmetry
In what order do the following orbitals fill: 2s, 3p, 4s, 4p, 4f, 5p, 5d, 6s? 2s, 4s, 3p, 4p, 5p, 6s, 4f, 5d 2s, 3p, 4s, 4p, 5p, 6s, 4f, 5d 2s, 3p, 4s, 4p, 4f, 5p, 5d, 6s 2s, 3p, 4s, 4p, 5p, 4f, 6s, 5d 2s, 3p, 4s, 4p, 6s, 5p, 4f, 5d
2s, 3p, 4s, 4p, 5p, 6s, 4f, 5d
triangle fold symmetry
3
What electronic configuration would you expect for a ruthenium cation in a ceramic (ionic) solid? (Assume Ru is in its most stable oxidation state) 2+ charge with electronic configuration: [Kr]5s04d5 3+ charge with electronic configuration: [Kr]5s05d5 3+ charge with electronic configuration: [Kr]5s04d6 3+ charge with electronic configuration: [Kr]5s04d5 2+ charge with electronic configuration: [Kr]5s04d6 2+ charge with electronic configuration: [Kr]5s05d6
3+ charge with electronic configuration: [Kr]5s04d5
pentagon fold symmetry
4
square fold symmetry
4
hexagonal fold symmetry
6
octagonal fold symmetry
8
Which of the following polymers do you think may form hydrogen bonds? (Feel free to Google the polymer structures.) A. Poly(acrylic acid), PAA B. Nylon 6 C. Polytetrafluoroethylene (PTFE, or "Teflon") D. Polypropylene A & B A & C A, B, & C All of the above
A & B
What type(s) of bonding would you expect in the common refractory ceramic Al2O3? (Choose the BEST answer). A mixture of ionic and metallic bonding. Covalent bonding van der Waals bonding Metallic Bonding A mixture of covalent and van der Waals bonding. Ionic bonding A mixture of ionic and covalent bonding.
A mixture of ionic and covalent bonding.
What do electrons do in a solid? A. Form the bonds between atoms. Both B & C Both A & C A, B, and C C. Determine the fluorescent properties of a material. Both A & B B. Determine the magnetic properties of a material.
A, B, and C
Base centered
A,B,C
Which of these bond types is/are directional? A. Covalent Bonds B. Ionic Bonds C. Metallic Bonds D. London Dispersion Forces A & B A & D All of the above
A. Covalent Bonds
HCP
ABAB
FCC
ABCABC
If AX and BX are both predominantly ionic solids and AX has a higher melting temperature than BX, what else might you predict about the properties of AX and BX? AX will have a lower coefficient of thermal expansion because the bond-energy curve has a deeper and more narrow energy well than the BX bond-energy curve. AX will be stiffer because the bond-energy curve has a shallower and broader energy well than the BX bond-energy curve. BX will be stiffer because the bond-energy curve has a deeper and more narrow energy well than the AX bond-energy curve. AX will have a higher coefficient of thermal expansion because the bond-energy curve has a deeper and more narrow energy well than the BX bond-energy curve. BX will have a lower coefficient of thermal expansion because the bond-energy curve has a deeper and more narrow energy well than the AX bond-energy curve.
AX will have a lower coefficient of thermal expansion because the bond-energy curve has a deeper and more narrow energy well than the BX bond-energy curve. The higher melting temperature makes AX have a deeper energy well--this makes it have a lower CTE (and also higher stiffness).
GaAs is a common semiconductor used to make solid state lasers used in CD and DVD players. How covalent are the bonds in GaAs? About 13% covalent About 3% covalent. About 91% covalent. About 97% covalent. About 87% covalent. About 9% covalent
About 97% covalent.
What are materials made out of
Atoms
The space group I4/m has what type of Bravais lattice? Body centered Base centered Primitive Symmetric Face centered
Body centered
Electrons are the primary atomic species contributing to:
Bonding - crystal structure - mechanical properties electronic properties optical properties magnetic properties
Considering the ionic nature of the Mg-O and Na-Cl bonds, which of the following statements do you agree with? A. Mg-O likely forms a stronger bond than Na-Cl because it is made between divalent ions rather than monovalent ions. B. Mg-O is likely a double bond while Na-Cl is likely a single bond. C. Assuming bond distances are about equal, Mg-O will likely form a 4x stronger bond than Na-Cl. Both A & B are likely true. Both A & C are likely true. Both B & C are likely true. All are likely true.
Both A & C are likely true.
The curvature of the Energy-bond distance curve has a direct phenomenological relationship to: A. The elastic modulus of a material. B. The yield strength of a material. C. The toughness of a material. D. The stiffness of a material. Both A & B Both A & C Both A & D A, B, & C. A, B, & D. A, B, C, & D.
Both A & D
These types of bonds share electrons between atoms. A. Ionic bonds B. Covalent bonds C. Metallic bonds D. van der Waals Bonds Both A & B Both B & C Both B & D
Both B & C
Which of the following can be used to estimate the depth of the energy well for a bond? A. The principle quantum number B. The enthalpy of fission C. The enthalpy of fusion Both A & C None of these.
C. The enthalpy of fusion
Which of the following elements would you expect to have the highest electronegativity? Cl Co Ge Ba Si
Cl
Which type(s) of bonding would you expect to find in the solid semiconductor germanium? Ionic bonding only. A mixture of covalent and van der waals bonding. A mixture of ionic and covalent bonding. Metallic bonding only. Covalent bonding only. A mixture of covalent and metallic bonding. Van der Waals bonding only.
Covalent bonding only.
Symmetry
Crystalline solids are those in which the atomic arrangement repeats itself Because of this repetition, we can use symmetry to simplify our description of the atomic arrangement in a solid. For example, all of the atoms in a close-packed solid are symmetrically identical, and therefore they all have the same coordination number.
he microstructure of materials: Crystalline "Grains"
Each grain is a single crystal of a material oriented in some "arbitrary" direction. Polycrystalline materials are formed by multiple grains with different arbitrary orientations impinging upon one another.
If a crystal structure is found to have all of its lattice parameters equal to one another (a = b = c), which crystal class might it belong to? A. Cubic B. Tetragonal C. Hexagonal D. Rhombohedral Either A or B Either A or C Either A or D
Either A or D
Covalent bonds
Electron(s) in the valence shell are shared between atoms Bonding is a result of orbital-orbital overlap (between unfilled, valence orbitals) Polymers and semiconductors usually have covalent bonds. Generally "stronger" than ionic or metallic bonds
ionic bonds
Electron(s) are transferred between atoms, forming ions Bonding is a result of cation (+) attracting anion (-) (i.e.,Coulombic attraction) Oxide ceramics are typically considered ionic solids, (& carbides, nitrides, & sulfides)
face centered
F
Based solely on their electronic configurations, which of these metals would you expect to have the largest saturation magnetization? (Assume no electrons are transferred between orbitals.) Iron Vanadium Manganese Zinc Palladium
Manganese
The intermetallic Al3Ni will PRIMARILY exhibit what type of bonding? Metallic "James Bond"ing Ionic Covalent van der Waals Hydrogen
Metallic
Inter axial angle
Physical angle between the three primary axes
Lattice parametr or lattice constant
Physical length of the side of unit cell (denoted here as: a, b, & c). These lengths are usually in angstroms or nanometers.
which orbital does most of the bonding in ionic solids plus metals
S orbitals
Why are ionic solids like most ceramics brittle? The need for bond directionality leads to fracture when the material is plastically deformed. Van der Waals bonds must be present to have non-brittle behavior. The non-directionality of bonding in ionic solids leads to fracture upon plastic deformation. The alignment of similarly charged ions upon plastic deformation leads to fracture.
The alignment of similarly charged ions upon plastic deformation leads to fracture.
grain boundaries
The boundaries between these misoriented single crystal grains are NOT well ordered
Coordination Number
The most basic descriptor for the arrangement of atoms in a solid is the "coordination number" of each atom. This is thenumber of nearest neighbor atoms surrounding a given atom.
microstructure
The size and relative orientation of grains
Unit cell
The smallest, repeatable unit that when translated in 3 chosen directions can cover all of space. This repeating pattern of unit cells forms the crystalline structure of a material.
Thermal energy of atoms in a system
Thermal energy of an atom KbT all atoms at T greater than 0 kelvin have non-zero energy this energy manifest mostly as atomic vibrations
Metallic bonds
Valence shell electron(s) are delocalized and shared across the ENTIRE solid. Bonding is a result of the atomic cores (nuclei + inner shells) "floating" in a " jellium" of valence electrons (also called: "electron sea" or "electron gas") Metals have metallic bonding (duh!)
Close-Packing: The Crystal Structure of (Many) Metals
We will start by studying the crystal structure of metals because they are the "simplest" to understand, a prototypical system, and have broad importance in engineering design. All solids desire an atomic packing arrangement that minimizes the total energy of the system Because metallic bonding is non-directional and all atoms are the same, metal atoms want to pack to maximize space filling a missing atom would reduce the average number of electrons in the electron sea and around neighboring atoms. These atoms would then be less satisfied and in a higher energy state
van der waals bonding
Weak attractions between atoms due to the polarity of other bonds (dipoles) AKA London Dispersion Forces, dipole-dipole bonding, hydrogen bonding, etc Dipole can be instantaneous (very, very weak) or permanent (a little stronger, e.g. H-bonds)
What is the expected electronic configuration of elemental (non-ionized) copper? [Ar] 4s23d9 [Kr] 4s13d10 [Ar] 4s13d10 [K] 4s23d9 [Ar] 4s13d10
[Ar] 4s13d10
Hexagonal
a=b/c A=B=90 Y=120 Primitive(P) ZuO CdS
Cubic
a=b=c A=B=Y=90 Primitive(P) body Centered(I) face Centered(F) NaCl Cu
Rhombohedral
a=b=c ; a=b=y /=90 Primitive(P) CaCO3
Crystal symmetry
all have some form of rotational symmetry This rotational symmetry must be concomitant with the ability to spatially translate and fill all space
Identity
all objects have identity, even the most assymmetric object have at least 1 symmetry
Bonding & Coefficient of Thermal Expansion (CTE)
assymetry of the atomic bonding potential energy well leads to a larger CTE rule of thumb: deeper potential energy wells are usually more symmetric and have lower CTEs increases change heat fusion decrease CTE
What determines the density of a material
atomic mass f the elements that make up the material --> composition how well the atoms pack into the solid --> crystal structure void space or porosity--> defects
Density
atoms actually contain a lot of empty space the nucleus contains most of the mass but it is only a small fraction an atoms' entire volume For example, while francium has an atomic weight that is 32x higher than lithium the difference in atomic size between francium and lithium is only about 2x therefore atomic mass is the primary factor in determining the density of a fully dense solid no porosity particularly in metals Crystal structure becomes more important for covalent and ionic bonded crystals, where the directionality of bonding forces more open structures
What happens if we plastically deform a metal?
atoms/bonds look the same sliding atoms by 1 atomic position does not change the bonding state
Rotational Symmetry
axis of rotation
Orthorhombic
a≠b≠c α=β=γ=90 Primitive(P) body Centered(I) Base Centered(C) face Centered(F) BaSO4 KNO3
Monoclinic
a≠b≠c α=γ=90° β≠90° Primitive(P) body Centered(I) Cimabar monoclinic
Triclinic
a≠b≠c α≠β≠γ Primitive(P) K2cr2O7
covalent bonds and directionality
covalent bonds are directional bonding requires maximizing orbital overlap therefore orbital shape is important
Tetragonal
crystal system: a = b ≠ c; α = β = γ = 90° Primitive(P) body Centered(I) TiO3
Because van der Waals bonding is about 100x weaker than other types of bonding (e.g., ionic, covalent, metallic), it has no influence on the properties of a material. true false
false
Positively charged ions are called anions. true or false
false
Simply shining infrared light onto an elemental metal can cause electron emission. True or false
false Infrared light is not of high enough energy to emit electrons from the bonding well in metals. Light in the UV range is of the appropriate energy, occasionally blue or purple visible light is sufficient.
Primitive(P)
forms of these crystals have lattice points("atoms") only at the corners
elastic modulus (E)
how much force is required to displace an atom from its equilibrium position higher slope = stiffer material smaller radius = greater curvature = greater stiffness
Body centered
i
Thermodynamics & Kinetics
if we know the barrier energy for this task, then we can compare this energy to the thermal energy of the atoms in the system. If thermal energy greater than barrier energy then the task is likely to happen
ionic bonding and directionality
ionic bonding is non-directional some bond energy regardless of orientation between two atoms
Lattice
is a regular collection of points in euclidean space
crystal structure
lattice plus basis
Mirror Symmetry
line symmertiy
What are the d-shells and f-shells good for
magnetism - d plus f orbitals are separate from bonding so they can act independently lots of unpaired electrons creates high spin - good saturation polarization, permanence Fluorescence + phosphorescence - crystal structures of a material can lead to induce orbitals in d or f shells to have different energies
Theoretical Density
mass of atoms in unit cell Multiply mass by number of atoms)/volume of unit cell
Metallic Bonds and directionality
metallic bonds are non directional most metals have s-orbitals as their valence shell--> spherical--> non directional symmetry
which orbital does most of the bonding in covalent solids
mix of s and p orbitals
covalent solid
more complex, "open", structures determined by fixed bonding angles
"Short Range Order" (SRO)
nearly all materials have SRO coordination number is a form
"Long Range Order" (LRO)
occurs in crystalline materials. LRO requires that each of the SRO units repeat their arrangement in 3-dimensional space.
Why is it ok for covalent bonds to have some orbital overlap
orbitals are not completely filled
Valence shell
outermost electronic shell determines the bonding
What types of orbitals exist in the n = 2 shell? (Choose ALL that apply) p-orbitals g-orbitals s-orbitals f-orbitals d-orbitals
p-orbitals s-orbitals
ionic solid
packing of spheres to maximization space filling(efficient packing)
ionic bonding and fracture
repulsion leds to fracture why most ceramics are brittle
basis
set of atoms for the crystal cructure
Space Group
set of symmetry elements which completely describe the spatial arraghement of a 3d periodic pattern
Bravais Lattices
showing lattice points not actual atoms
Which material has a higher elastic modulus
steeper slope, less room to stretch at a finite temperature
What does the principle quantum number(n) tells us
the electrons distance from the nuclues
What happens when we heat up a gas
the gas molecules move faster, gain more energy, increase velocity, increase KE
center of inversion
there is always a matching part, which has the same distance from a central point but in opposite direction
core shells
these electrons are usually not involved in bonding
unit cell
translational symmetry smallest posrtion of the atomic arrangement which, if repeated in 3 dimensions, will form the entire atomic arragment of the solid
Why do polymers have such low elastic moduli?
van der waals holding chains together
hydrogen Bonding
very electronegative element which monopolizing the electrons
