matsci2
The wavelengths of x-rays are similar in size to... ...an electron. ...the wavelength of IR radiation. ...grains in polycrystalline materials. ...the spacing between crystal planes in a material. ...the width of a human hair.
...the spacing between crystal planes in a material.
Covalent bonds... ...are non-directional because they require the overlap of spherical orbitals. ...are directional because they require the overlap of non-spherical valence orbitals. ...are directional because they share electrons. ...are non-directional because they share electrons.
..are directional because they require the overlap of non-spherical valence orbitals.
how many lattice points in the primitive unit cell?
1
What is the charge state and electronic configuration for Cu in the ceramic materials Cu2O?
1+, [Ar] 4s0, 3d10
What is the charge state and electronic configuration for Cu in the ceramic materials Cu2O? 2+, [Ar] 4s1, 3d10 1+, [Ar] 4s1, 3d10 2+, [Ar] 4s0, 3d9 2+, [Ar] 4s0, 3d10 1+, [Ar] 4s0, 3d10
1+, [Ar] 4s0, 3d10
For a cubic unit cell, how many planes are in the {110} family?
12
how many lattice points in the body centered unit cell?
2
How many planes are in the {100} family of planes in an orthorhombic unit cell? 12 2 1 4 none 6
2 (100) and (-1,00)
If the lattice parameter for a cubic crystal is 6 angstroms, what is the interplanar spacing for the (221) planes? It depends on the location of the origin point. 2 angstroms 1 angstrom 1.2 angstroms 3 angstroms 0.67 angstroms
2 angstroms why? Use d(hkl) = a / (h^2+k^2+l^2)^(1/2)
if a lattice point is positioned on the "face" of a unit cell, amongst how many different unit cells is that lattice point shared
2 unit cells (one have in the current cell and the other half in the other)
Tellurides are interesting semiconducting materials that are useful for photovoltaics. What effective charge would you expect tellurium to adopt when it bonds to a metal to form a "metal telluride"? 3+ 1+ 2- 3- 1- 2+
2-
In a cubic unit cell, which of the following x-ray diffraction peaks will have the largest Bragg diffraction angle (2theta)? 220 111 301 003 221
301 why? bc h^2+k^2+l^2 and 10 is the largest value
In what order do the following orbitals fill?3s, 3d, 4s, 4d, 4f, 5s
3s, 4s, 3d, 5s, 4d, 4f
how many lattice points in the face centered unit cell?
4
What is the expected electronic configuration of elemental (non-ionized) copper? 1. [Ar] 4s13d10 2. [K] 4s23d9 3. [Ar] 4s23d9 4. [Ar] 4s13d10 5. [Kr] 4s13d10
4. [Ar] 4s13d10
To which point group does the space group I4mm belong?
4mm
Which of the following crystal class(es) must have lattice parameters sof equal length in all 3 primary crystallographic directions (i.e., a=b=c)? 1. cubic 2. hexagonal 3. Rhombohedral 4. both 1 and 2 5. both 1 and 3
5. both 1 and 3
which orbital(s) most likely contributes electrons to the "electron sea" in the metal molybdenum 4s 5s 4d 5d both 4s and 4p
5s why?
If a tetragonal unit cell has "a" lattice parameters of 5 angstroms in length and a "c" lattice parameter of 2 angstroms in length, then the unit cell volume would be:
5x10-23 cm3
Tantalum's electronic configuration is [Xe] 6s^2 4f^14 5d^3
6s
what is the outer most electronic orbital (valence shell) for barium?
6s
if thermal energy of atoms (>/<) barrier energy then the task is likely to happen
> greater than
Iridium is best classified as: A transition metal An alkaline earth element A noble gas A halogen A rare earth element.
A transition metal
What types of orbitals exist in the n = 3 electronic shell of an atom? (select all that apply) A. s-type orbitals B. p-type orbitals C. d-type orbitals D. f-type orbitals
A, B, and C (s-, p-, and d-type orbitals)
For a tetragonal unit cell with lattice parameters: a, b = 4 angstroms c = 6 angstroms Which of the following x-ray diffraction reflections will occur at the SMALLEST Bragg diffraction angle? A. 100 B. 001 C. 010 Both A & B will have equivalently small diffraction angles. Cannot be determined from the given information.
B. 001 why? Because this is orthorhombic, the (100), (010), and (001) are not in the same family of planes, so they all have different spacing. Because the c-axis has the smallest lattice parameter, it will have the largest Bragg diffraction angle
Which of these elements would you expect to have the smallest electronegativity? Chlorine Strontium Fluorine Sodium Barium
Barium
The space group Cmmm has what lattice type?
Base centered bc C stands for body-centered
These types of bonds do not really share any electrons between the bonding atoms. (Sharing means a single electron could be associated with more than one atom; it actively changes its association while being bonded in the solid.) (select all that apply) A. Ionic bonds B. Covalent bonds C. Metallic bonds D. van der Waals Bonds
Both A and D
The peaks observed in an x-ray diffraction experiment are the result of:
Constructive interference from x-rays scattering from planes of atoms with a path length difference equal to the wavelength of the x-rays.
The peaks observed in an x-ray diffraction experiment are the result of: Constructive interference from x-rays scattering from planes of atoms with a path length difference equal to the wavelength of the x-rays. Absorption of x-rays from excitation of core shell electrons in the material. Constructive interference from x-rays scattering from planes of atoms with a path length difference equal to half of the wavelength of the x-rays. Destructive interference from x-rays scattering from planes of atoms with a path length difference equal to the wavelength of the x-rays. Destructive interference from x-rays scattering from planes of atoms with a path length difference equal to half of the wavelength of the x-rays. Emission of x-rays due to the relaxation of core shell electrons in the material.
Constructive interference from x-rays scattering from planes of atoms with a path length difference equal to the wavelength of the x-rays.
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.) Zinc Manganese Vanadium Palladium Iron
Manganese
The intermetallic Al3Ni will PRIMARILY exhibit what type of bonding?
Metallic
which bond will have the larger bond strengths: Na-Cl or Mg-O?
Mg-O: why? Mg^2+ and O^2- vs Na^+ and Cl^- higher degrees and |Z*Z|=|2*2|=4 vs 1
What does it mean if a crystal structure has 3-fold rotational symmetry? a. The crystal structure will look the same before and after a rotation of 3° around this axis of symmetry. b. The crystal structure will look the same before and after a rotation of 120° around this axis of symmetry. c. Three different axes of symmetry rotation are available to replicate the structure. d. The crystal structure will look the same before and after rotating it 3 times in any direction. e. The crystal structure will look the same before and after rotating it 60° around this axis of symmetry.
The crystal structure will look the same before and after a rotation of 120° around this axis of symmetry.
Which of these is the proper Miller Indices notation for the direction "113"? -113- 113 [113] [113> <113> {113} (113)
[113]
What is the expected electronic configuration of elemental (non-ionized) copper?
[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
define rotational symmetry
all crystals have some form of rotational symmetry. this rotational symmetry must be concomitant with the ability to spatially translate and fall all space
The space group I4mm is of what lattice type?
body centered bc I stands for body centered
Which of the following statements about the repulsive force felt between two bonding atoms is/are true: a. the pauli exclusion principle contributes to the repulsive force. b. the force-bond distance curve is the multiplication product of the repulsive force curve and the attractive force curve c. as 2 atoms get closer to one another, the repulsive force ALWAYS becomes larger in magnitude than the attractive force
both a & c are correct
Cobalt can have either an FCC or HCP structure. At room temperature, how would you expect the mass densities of the FCC and HCP forms of cobalt to compare? a. The density of FCC cobalt will be GREATER THAN the density of HCP cobalt. b. The density of FCC cobalt will be LESS THAN the density of HCP cobalt. c. The density of FCC cobalt will be EQUAL TO the density of HCP cobalt.
c. The density of FCC cobalt will be EQUAL TO the density of HCP cobalt. why? FCC and HCP have the same atomic packing density, so if the atom's are of the same type, the mass density should be the same.
A metal with a face-centered cubic crystal structure is composed of... a. close-packed planes with 4-fold rotational symmetry that repeats in a stacking sequence of ABAB... b. close-packed planes with 6-fold rotational symmetry that repeat in a stacking sequence of ABAB... c. close-packed planes with 6-fold rotational symmetry that repeat in a stacking sequence of ABCABC... d. non-close-packed planes with a repeating stacking sequence of ABAB... e. close-packed planes with 4-fold rotational symmetry that repeat in a stacking sequence of ABCABC... f. non-close-packed planes with a repeating stacking sequence of ABCABC...
c. close-packed planes with 6-fold rotational symmetry that repeat in a stacking sequence of ABCABC...
tetragonal
crystal system: a = b ≠ c; α = β = γ = 90° Primitive(P) body Centered(I) TiO3
For the force-distance curve between two bonding atoms shown here, which feature best represents the equilibrium bond distance?
distance R0
define grain in the context of crystalline microstructures
each grain is a single crystal of a material oriented in some "arbitrary" direction
The volume of an atom is mostly composed of Correct answer: a. Empty space b. The nucleus c. Neutrons d. Protons e. Electrons
empty space
True or False: Most man-made crystalline materials are single crystals, not polycrystalline.
false
Van der Waals bonding is so weak that it serves no purpose in engineering design.
false
true or false: Positively charged ions are called anions.
false why: positive=cation negative=anion
True or False: If Laue diffraction is performed on two different cubic crystal materials with the same space group, the crystal with the smaller lattice parameter will have the closer arrangement of diffraction spots.
false why? A smaller lattice parameter means that the interplanar spacing is smaller, which means the diffraction angle (and therefore the separation of spots) is greater
(True/False) The following notation is used to describe a family of planes: < h k l >
false answer: {h k l}
The bonds between Fe-Fe in a steel alloy are primarily considered to be covalent.
false: This is a bit tricky. Even when metallic elements bond to themselves, you still get primarily metallic bonding with the "bonding electrons" delocalized in the "electron sea". You do not form covalent bonds, although they may have a minor covalent character--more so if it is an intermetallic.
what is the magnetic quantum number (m)
gives the number of orbitals, for each subshell(l) and their unique orientation m has values of 1>m>-1; thus, the total number of orbitals in a subshell is (2l+1)
how to determine if bond is ionic
if electronegativity is greater than 2.0
example of when van der waals is important
in the example of animals like geckos walking up waals or other bugs walking on water
electronegativity trend
increases up and to the right
the crystal structure of a material = _ and _
lattice and basis
how is the energy bond curve used to predict melting temperature?
look at depth of potential energy well. the one with the rounded part closer to when energy=0 will have a lower melting temperature, and vice versa. why? barrier energy to melt the solid is the distance from the energy axes to the bottom of the well... ie effectively the amount of energy (temp) required to break the bonds that hold the solid together ( which will only get higher the more energy required and the deeper the well.
how is the energy bond curve used to predict coefficient of thermal expansion?
look at the symmetry of the curves. the curve that is less symmetric has a higher CTE * rule of thumb: deeper potential energy wells are usually more symmetric and have lower CTEs
What are some special qualities of d-shells and f-shells?
magnetic behavior comes from core shell behavior of d and f orbitals creates high magnetic spin=> magnetic properties (due to unpaired electrons)
because the metallic bonding is nondirectional and all atoms are the "same" metal atoms want to pack to (minimize/maximize) space filling
maximize
The intermetallic Al3Ni will PRIMARILY exhibit what type of bonding? Covalent Metallic Hydrogen van der Waals Ionic "James Bond"ing
metallic
all solids desire an atomic packing arrangement that (minimizes/ maximizes) the total energy of the system
minimizes
Body Centered Cubic (BCC)
not close-packed
what happens if we plastically deform a metal?
not much: all atoms/ bonds look the same throughout the entire metal. sliding one atom unit down makes no difference in bonding
define lattice parameter
or lattice constant: which is the physical length of the side of a unit cell (denoted here as: a, b, & c). These lengths are usually in angstrom or nanometers
The numbers and hands on this wristwatch will continue to "glow green" for an hour or more without any further stimulation. This is an example of what phenomenon? a. phosphorescence b. fluoresce
phosphorescence
differentiate between van der waals bonding and H-bonding specifically in polymers
polymers are held together largely by van der waals bonding
what are the primary and secondary bonds?
primary= ionic, covalent, and metallic secondary= van der waals, h-bonding, etc.
describe the features of covalent bonds: directionality, relative strength, and whether electrons are transferred or shared
share electrons 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 yes, they are directional bc bonding requires maximizing orbital overlaps and orbital shape is important ( ie in the case of SP3 hybridized)
what is the magnetic spin quantum number (ms)
spin quantum number is either +1/2 or -1/2 and reflects the different electronic spins (2e- per orbital)
how is the energy bond curve used to predict stiffness?
stiffness can be seen on a curve by looking a the radius of curvature (ie the region from 4 to 2 in the diagram) *the smaller radius of curvature= greater stiffness
To which crystal class does the space group I4mm belong? hexagonal orthorhombic cubic rhombohedral monoclinic tetragonal
tetragonal why? So if the first number in the point group is a "6", then it is a hexagonal type crystal. If the first number is a "4" like here ("4mm"), then tetragonal -- because it has that 4-fold rotational symmetry down the c-axis (the (001) type plane is a "square"; so it has four-fold symmetry). For cubic, there is a 3 in the second position of the point group, like "m3m". (This means that there are 3-fold symmetry axes down all of the body diagonals of the cube -- which is "higher symmetry" than just the 4-fold rotational symmetries of all the sides -- i.e., tetragonal does NOT have these 3-fold axes down its body diagonals).
define grain boundaries in the context of microstructures of crystalline grains
the boundaries between these mis-oriented single crystal grains are NOT well ordered
When given multiple curves on a force-bond curve, how do you determine which material will have the highest elastic modulus?
the curve with the steeper slope of elastic portion
what is the principle quantum number (n)
the electronic shell... n is assigned an integer (1,2,3,...) that refers to the quantum shell. quantum shell is a set of fixed energy level that electrons belong K: n=1, L: n=2, M:n=3
what happens when we heat up a gas?
the gas molecules move faster and gain kinetic energy *temp=how much energy atoms have *higher velocity=higher kinetic energy
Define Polycrystalline in the context of microstructure of materials
they are formed by multiple grains with different arbitrary orientations negatively impacting one another most polycrystalline materials have grains that are microscopic
describe the features of ionic bonds: directionality, relative strength, and whether electrons are transferred or shared
transfer electrons strength: weaker than covalent bonds No: ionic bonds are non-directional... ie ionic bonds will have the same bonding energy independent of the orientation of the 2 atoms /ions (electrostatic attraction does NOT depend on direction)
(True/False) X-ray diffraction can be used to determine the atomic spacing between crystalline planes in a solid.
true
Because of their rigid bonding angles, covalent solids usually have more open crystal structures than ionic solids.
true
True/False) As elements increase in atomic number, their atomic masses tend to increase more quickly than their atomic volumes.
true
True/False: One-fold (1-fold) rotational symmetry is permitted in crystal structures.
true
true or false: Because of their rigid bonding angles, covalent solids usually have more open crystal structures than ionic solids.
true
true or false: Grain boundaries are the boundaries between two mis-oriented single crystals in a polycrystalline solid.
true
define translational symmetry
we can define a unit cell if repeated in 3D, will form the entire atomic arrangement of the solid
In an Energy-Bond Distance curves, how do you determine which material has the highest thermal expansion coefficient?
whichever is widest from 4 to 3 in the diagram shown. Ie which has the greatest distance from one side of the parabola to the other
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)
A material will have a high elastic modulus if its Energy-Bond Distance curve exhibits: 1. a small radius of curvature and a large second derivative at the global minimum of the plot. 2. a small radius of curvature and a small second derivative at the global minimum of the plot. 3. a large radius of curvature and a small second derivative at the global minimum of the plot. 4. a large radius of curvature and a large second derivative at the global minimum of the plot.
2. a small radius of curvature and a large second derivative at the global minimum of the plot.
In what order do the following orbitals fill? 3s, 3d, 4s, 4d, 4f, 5s
3s, 4s, 3d, 5s, 4d, 4f
Consider the atoms on the surface of a piece of metal that has an HCP crystal structure. Assuming the surface atoms are part of a close-packed plane, what would be the coordination number for one of these atoms?
9 fold coordination: At the surface, the row atomic "upper" atomic plane is missing. This include 3 of the 12 nearest neighbor atoms that are typically found in the bulk of an HCP structure. Therefore, these surface atoms only have 9-fold coordination. This loss of "3 bonding atoms" is what creates "surface energy".
in the equation E=-A/X^m + B/X^n, which is the repulsive and attractive force?
A= attractive B= repulsive
stacking of HCP
ABA
Stacking of FCC
ACBA
Metallic bonds... A. ...allow for high electrical conductivity in a material. B. ...are non-directional. C. ...allow a material to plastically deform. Both A & B Both A & C Both B & C All of the above (A, B, & C)
All of the above (A, B, & C)
Barium is best classified as: A noble gas An alkaline earth element A transition metal A rare earth element. A alkali metal
An alkaline earth element
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.
These types of bonds do not really share any electrons between the bonding atoms. (Sharing means a single electron could be associated with more than one atom; it actively changes its association while being bonded in the solid.) A. Ionic bonds B. Covalent bonds C. Metallic bonds D. van der Waals Bonds Both A & B Both B & C Both A & D A, B, and D B, C, and D
Both A & D
in the bond energy equation: Etotal = -A/x + B/x12 A. -A/x describes the energy of attraction between the two atoms forming the bond B. -A/x describes the energy of repulsion between the two atoms forming the bond C. B/x12 describes the energy of attraction between the two atoms forming the bond D. B/x12 describes the energy of repulsion between the two atoms forming the bond Both B & C are true. Both A & D are true.
Both A & D are true.
Which type(s) of bonding would you expect in the plastic material high-density polyethylene? (Choose the BEST answer.) Both ionic and van der Waals bonding. Both covalent and van der Waals bonding. Van der Waals bonding only Covalent bonding only Ionic bonding only. Metallic bonding only Both ionic and covalent bonding
Both covalent and van der Waals bonding. why: Polymers typically have covalent bonding in the backbone and van der Waals bonding between polymer chains.
What types of orbitals exist in the n = 3 electronic shell of an atom? A. s-type orbitals B. p-type orbitals C. d-type orbitals D. f-type orbitals E. Both A & B (s- and p-type orbitals) F. A, B, and C (s-, p-, and d-type orbitals) G. A, B, C, and D (s-, p-, d-, and f-type orbitals)
F. A, B, and C (s-, p-, and d-type orbitals)
what's the difference between fluorescence and phosphorescence?
Fluorescence=fleeting/ immediate fading of glowing light phosphoresce= excited state lasts longer and material glows longer (ex: glowing stares we had as kids)
how to determine coordination number
In a unit cell, an atom's coordination number is the number of atoms it is touching. 1. The hexagonal closest packed (hcp) has a coordination number of 12 and contains 6 atoms per unit cell. 2. The face-centered cubic (fcc) has a coordination number of 12 and contains 4 atoms per unit cell.
The space group p622 has (1) what type of lattice and (2) what type of point group symmetry?
It is a primitive lattice (can tell by the p in front of the numbers) and has the 622 type of point group symmetry
when given multiple curves on a bond-energy curve chart, how do you determine which curve has the longest equilibrium bond length at 0K?
Look for which curve has the minimum farthest from the origin (0) ( ie the lowest part of the curve is farthest to the right), and therefore is the longest bond length.
difference between SRO and LRO
SRO: coordination number is a form of "SRO". Nearly all materials have SRO LRO: occurs in crystalline materials. LRO requires that each of the SRO units repeat their arrangement in 3D space
Below are two plastic cups both made out of the polymer, (C8H8)n. Between styrofoam and a polystyrene cup, which do you expect to be less dense and why? a. The polystyrene cup is likely less dense because it has more porosity than the styrofoam cup. b. The styrofoam is likely less dense because it is made of lower atomic number elements. c. The polystyrene cup is likely less dense because it is made of lower atomic number elements. d. The cups likely have the same density because they are made out of the exact same polymer. e. The styrofoam cup is likely less dense because making the polymer into a foam adds more porosity to the material.
The styrofoam cup is likely less dense because making the polymer into a foam adds more porosity to the material.
what is the electron configuration for elemental Ti
[Ar] 4s^2 3d^2
Which of the following folds of symmetry can fill all of space? (answer can involve more than one) a. 2 fold b. 3 fold c. 4 fold d. 5 fold e. 6 fold f. 8 fold g. 1 fold
a. 2 fold b. 3 fold c. 4 fold e. 6 fold g. 1 fold
what determines the density of a material?
atomic mass is the primary factor determining the density side notes* atomic mass of the elements that make up the material=> composition how well the atoms pack into the solid=> crystal structure void space or porosity: defects=> very common in natural products like wood & foams (polymers & ceramics)
thermal energy of an atom manifests itself as ___ ___
atomic vibrations
Orthrombic
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
what do electrons for a solid?
electrons are the primary atomic species contributing to 1. bonding=> crystal structure, mechanical properties, and more 2. electronic properties 3.optical properties 4. magnetic properties. electrons do 90% of the work in a material
true or false: The bonds between Fe-Fe in a steel alloy are primarily considered to be covalent.
false why: This is a bit tricky. Even when metallic elements bond to themselves, you still get primarily metallic bonding with the "bonding electrons" delocalized in the "electron sea". You do not form covalent bonds, although they may have a minor covalent character--more so if it is an intermetallic.
true or false: Van der Waals bonding is so weak that it serves no purpose in engineering design.
false why: think about the purpose of van der waals interactions with animals/bugs that walk on water or climb up walls
True/False: A unit cell is ANY portion of a crystalline lattice that if translated in three-dimensional space would form the entire lattice structure.
false: A unit cell is not just ANY portion of the lattice but rather the SMALLEST portion of the lattice that if translated would form the entire lattice structure.
which type of bonding listed below would best support high electrical conductivity in a material? covalent bonding metallic bonding van der waals bonding ionic bonding
metallic bonding. why? the electrons shared in metallic bonding are shared throughout the entire material. this ability for these electrons to traverse the entire material is why metals have high electrical conductivity
what are the 4 lattice types?
primitive, body centered, base centered, face centered
structure of an atom
protons, neutrons, electrons
this crystal class has lattice parameters that are all the same and interaxial angles that are all the same but are NOT 90degrees
rhombohedral
The _ and relative ___ of grains is mostly what constitutes a material's microstructure.
size ; orientation
quantum numbers define the _ and _ of the electron cloud around a given atom's nucleus
size and shape
define unit cell
smallest, repeatable unit that when translated in 2 chosen directions can cover all space
describe the features of metallic bonds: directionality, relative strength, and whether electrons are transferred or shared
strength: strong but weaker than covalent bonds in polymers and semiconductors 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) type: metals have metallic bonding valence shell electrons are delocalized and shared across the entire solid non-directionality bc nearly all metals, the valence shell is an s-orbital => spherical s-shell=> overlap will have the same electron density in all directions
describe the features of van der waals bonds: directionality, relative strength, and whether electrons are transferred or shared
strength: weak attractions between atoms due to the polarity of other bonds (dipoles) directionality: non-directional share or transfer AKA london dispersion forces, dipole -dipole bonding, h-bonding, etc... dipole can be instantaneous (very, very weak) or permanent (a little stronger e.g. H-bonds_
what is the azimuthal quantum number (L)
subshell/orbital type... l is assigned numbers from l=0 to (n-1); tells us the type of orbital l=0: s orbital l=1: p orbital l=2: d orbital l=3: f orbital l=4: g orbital
why do polymers have such low elastic moduli?
van der waals bonding holds most of the chains together in a polymer solid=> many interaction points, but weak, but do add up
