chem chapter 12
body centered cubic, BCC
(BCC/FCC/primitive cubic) metals include Fe, Cr, Na, and W
1. covalent bonds are stronger than dispersion forces 2. the crystal lattice in this allotrope is significantly more ordered than in the other
2 reasons why diamond is considered stronger than graphite
1. double bonds are stronger than single bonds 2. the comparison of allotrope strength is made at similar lattice sizes
2 reasons why graphene is considered stronger than diamond
semiconductor; insulator; absorbs; lower; lower
A yellow-orange compound is more likely to be a __________ while a white one is more likely to be an __________. The yellow-orange compound ________ light in the visible spectrum, whereas the white compound does not. This indicates that the yellow-orange compound has a _______ energy electron transition than the white one. Semiconductors have _______ energy electron transitions than insulators.
lower; lower; increase
Although periodic trends tend towards (lower/higher) electronegativities as you go down a group, there are exceptions. In group 2B (12), although aluminum does have a (lower/higher) electronegativity than boron, after aluminum electronegativity values (increase/decrease) slightly from aluminum to gallium to indium.
Mg 2+
An important type of porphyrin is chlorophyll. What is the central metal ion in chlorophyll?
increases; more, higher, lower
Decreasing the size of a semiconductor (increases/decreases) the band gap, which means that ________ energy is required to excite an electron from the valance band to the conduction band, so a (lower/higher) frequency and (lower/higher) wavelength would be absorbed.
Atomic radii and chemical bonding properties
For a substitutional alloy to form, the two metals combined must have similar
Al>Ga>B to answer this question, you need to consider the electronegativity of the atom. The valence band and conducting bands get closer in energy as the nucleus becomes less electronegative. more overlap=greater conductivity
Rank the elements aluminum, gallium, and boron in order of decreasing conductivity. explain how/why
lowest: ice (bc its a molecular solid) middle: potassium iodide (bc it's an ionic solid) highest: quartz (because it's a covalent-network solid)
Rank the following solids from lowest to highest melting point: potassium iodide, quartz, and ice (solid water). explain why
the sum of the capacities of the overlapping bands.
The capacity of the composite band is
These ligands can simultaneously occupy two or more sites in a coordination sphere of the metal.
What specific behavior do chelating ligands possess?
graphene
Which form of carbon is two-dimensional and can sustain electrical current densities six orders of magnitude higher than those sustainable in copper?
the same atom; impossible; different atoms; are not
Why can ethylenediamine (en) act as a bidentate ligand whereas water cannot? Answer: The nonbonding electron pairs in H2O are located on ___________, which makes it (possible/impossible) for both pairs to be donated to the same metal atom. To act as a chelating agent the nonbonding electron pairs need to be located on _________ that _______connected to each other.
Amorphous silica does not pack as efficiently in three dimensions when compared to the atoms in quartz. Crystalline quartz has a regular repeating structure in all three directions, whereas amorphous silica has a loose disordered structure that contains spaces throughout.
]Amorphous silica, SiO2, has a density of about 2.2 g/cm3, whereas the density of crystalline quarts, another form of SiO2, has a density of 2.6 g/cm3. What is the best explanation for the difference in density?
hexagonal and face-centered are tied, then body centered, then simple cubic
arrange the following in order from most efficient use of space to least efficient use of space: body-centered cubic, hexagonal close packing, simple cubic, face-centered cubic
covalent bonds; weaker intermolecular forces
atoms within a chain in a polymer are held together by ____________, while adjacent chains are held together largely by ___________
~3.5eV; insulator
band gaps greater than _________ are so large that the material is not a semiconductor; it is an _________ and doesn't conduct electricity.
-1
charge on SCN
increases, decreases
decreasing the size of a semiconductor (increases/decreases) the band gap, which (increases/decreases) the wavelength of light emitted
1 and 4- diamond 2,3, and 5- graphite
determine which of the 5 listed properties belongs to diamond and which belong to graphite: 1. greater density 2. more dispersion forces 3. greater number of pi bonds 4. greater hardness 5. greater electrical conductivity
they do NOT have a random structure (gasses do) but they just don't have regular repeating patterns
do amorphous solids have random structures
amorphous materials (especially glasses) don't break in clean lines, instead break and create random shapes
explain how amorphous solids break
simple, and can be generated by placing a simple atom on each lattice point in either primitive cubic lattice, BCC, or FCC
explain the crystal structures of many metals
crystalline solids have well-defined flat surfaces or faces that make definite angles with one another; the orderly arrangements of atoms that produce these faces cause the solids to have highly regular shapes. amorphous solids lack this order and have a less defined, un-ordered macroscopic structure
explain the difference in appearance between crystalline and amorphous solids at the macroscopic level
Continuous energy bands of molecular orbitals require a large number of atoms contributing a large number of atomic orbitals to the molecular orbital scheme. If a solid has dimensions 1-10 nm, nanoscale dimensions, there may not be enough contributing atomic orbitals to produce continuous energy bands of molecular orbitals.
explain why "bands" may not be the most accurate description of bonding in a solid when the solid has nanoscale dimensions
ρNi3Al= [1 molecule Ni3Al/(3.56×10−8 cm)^3] × [1 mol Ni3Al/6.022×10^23 molecules Ni3Al] × [203.062 g/1 mol Ni3Al]
give the equation to solve for the density of Ni3Al given that it is FCC with an edge length of 3.56 Å
ρNi=[4 atoms Ni/(3.53×10−8 cm)^3] × [1 mol Ni/6.022×10^23 atoms Ni] × [58.6934 g/1 mol Ni]
give the equation to solve for the density of pure nickel given that it is FCC with an edge length of 3.53 Å
The abbreviation ppm stands for parts per million. Find a fraction of units in which the denominator is one-million times the numerator. For example, if we have a certain number of kilograms of a mixture and want to find how much of a component that has a concentration of 2.00 ppm is present, we might convert ppm to mg/kg, because 1 kg is one million times 1 mg.
how do you identify alternative units for ppm? using kg as the desired unit for example
motif
in most crystals, the atoms are not exactly coincident with the lattice points. instead, a ___________ is associated with each lattice point
rhombic lattice
in what 2D lattice does a=b and γ is arbitrary
hexagonal lattice
in what 2D lattice does a=b, and γ is 120 degrees
square lattice
in what 2D lattice does a=b, and γ=90 degrees
rectangular lattice
in what 2D lattice does a≠b, and γ is 90 degrees
oblique
in what 2D lattice does a≠b, and γ is arbitrary
cubic
in what 3D lattice does a=b=c and α=β=γ
rhombohedral
in what 3D lattice does a=b=c and α=β=γ≠90degrees
hexagonal
in what 3D lattice does a=b≠c and α=β=90degrees, γ=120 degrees
tetragonal
in what 3D lattice does a=b≠c and α=β=γ=90degrees
orthorhombic
in what 3D lattice does a≠b≠c and α=β=γ=90degrees
monoclinic
in what 3D lattice does a≠b≠c and α=γ=90 degrees, β≠90degrees
triclinic
in what 3D lattice does a≠b≠c and α≠β≠γ
polonium
metals with primitive cubic structure are rare, one example being
1
number of donor atoms on CN- ligand
1
number of donor atoms on CO ligand
1
number of donor atoms on Cl- ligand
6
number of donor atoms on EDTA 4- ligand
1
number of donor atoms on F- ligand
1
number of donor atoms on H2O ligand
1
number of donor atoms on NH3 ligand
2
number of donor atoms on gly- ligand
1
number of donor atoms on ligand Br-
2
number of donor atoms on ligand CO3 2-
0.1
one Å equals _____ nm
more
polymers are (more/less) flexible than metallic, ionic, or covalent-network-solids.
not malleable or ductile (brittle), insulators, high melting point
properties of ionic solids (malleable/ductile, conductivity, melting point, soft/hard)
malleable, ductile, electrical and thermal conductivity, lustrous, high melting point, soft
properties of metallic solids (malleable/ductile, conductivity, melting point, soft/hard)
molecular<metallic<ionic<covalent
rank 4 types of solids from lowest to highest melting point
sigma AND pi bonds; only sigma bonds'; poor; insulating
sheets, tubes, and spheres are only possible when the atoms are connected by _________. in a network of SiO2, the atoms are connected by ________. given the structures of pure silicates, they are (good/poor) lubricants and are electrically (conductive/semi-conductive/insulating)
valence band; conduction band; valence; conduction; band gap; electron voltes (eV); 1.602 x 10^-19
the band that forms from bonding molecular orbitals is called the __________, and the band that forms the antibonding orbitals is called the ________. in a semiconductor, the _________ band is filled with electrons and the ________ band is empty. these two bands are separated by the _________. in the semiconductor community, energies are given in ___________, one of which is equal to _______ Joules.
covalent bonds; the nuclei of atoms must be closer together to share electrons
the distance between atoms is shorter in (intermolecular forces/covalent bonds) because ____________
the charges of the metal and all the ligands
the overall charge of a complex is the sum of _________
1. the size and shape of the unit cell 2. the locations of atoms within the unit cell
the structure of a crystalline solid is defined by
true! covalent bonding is in molecular solids, but molecules themselves held together with weak forces
true or false: there is covalent bonding in both molecular and covalent-network solids
1. electrical conductivity 2. ability to be strong without being brittle
what 2 properties does metallic bonding give metals
their form of bonding--a delocalized sea of electrons
what allows metals to conduct electricity
solids whose molecular arrangement lacks the order (regularly repeating long-range pattern) of a crystal. may have short-term order in an area but not overall.
what are amorphous solids
solids that are held together by an extended network of covalent bonds
what are covalent network solids
solids that are held together by the mutual electrostatic attraction between cations and anions
what are ionic solids
points in a crystal, all of which have identical environments
what are lattice points
the vectors a, b, and c that define each lattice point in a crystal lattice. beginning from any lattice point, it is possible to move to any other lattice point by adding together whole-number multiples of the two lattice vectors
what are lattice vectors? how do they connect lattice points
solids that are composed of metal atoms held together by a delocalized "sea" of collectively shared valence electrons
what are metallic solids
solids that are composed of molecules held together by their intermolecular forces
what are molecular solids
a solid whose dimensions range from 1 to 100 nm and whose properties differ from those of a bulk material with the same composition. the properties of conventional materials change when their crystals become this small
what are nanomaterials? how do they relate to conventional materials
large molecules with long chains of atoms (usually carbon), where the atoms within a given chain are connected by covalent bonds and adjacent chains are held to one another largely by weaker intermolecular forces
what are polymers
cubic, tetragonal, orthorhombic, rhombohedral, hexagonal, monoclinic, triclinic
what are the primitive 3D lattice types
oblique, square, rectangular, hexagonal, rhombic
what are the types of 2D unit cell shapes
a crystal lattice in which the lattice points are located at the center and corners of each unit cell
what is a body-centered lattice
solids whose internal arrangement of atoms, molecules, or ions possesses a regularly repeating pattern in any direction through the solid.
what is a crystalline solid
a crystal lattice in which the lattice points are located at the faces and corners of each unit cell
what is a face-centered lattice
in a crystal, the group of atoms associated with each lattice point
what is a motif
a crystal lattice in which the lattice points are located only at the corners of each unit cell
what is a primitive lattice
the smallest portion of a crystal that reproduces the structure of the entire crystal when repeated in different directions in space. it is the repeating unit or building block of the crystal lattice.
what is a unit cell
covalent-network bonding
what is responsible for the unique properties of semiconductors
γ (gamma)
what is the angle between a and b vectors in a 2D lattice called
the geometrical pattern of points on which the unit cells are arranged; in effect, an abstract scaffolding for the crystal structure
what is the crystal lattice
period 5 and 6 elements in each group have very similar radii and chemical properties
what is the effect of the lanthanide contraction
the gradual decrease in atomic and ionic radii with increasing atomic number among the lanthanide elements, atomic numbers 57-70. the decrease arises due to a gradual increase in effective nuclear charge thru the lanthanide series. this happens bc as each proton is added to the nucleus going down the line, the extra electron is added to the 4f orbital which is the inner shell so its not as effective at shielding the positive charge of the nucleus so the e- cloud is pulled in closer and closer in the series with increasing atomic number
what is the lanthanide contraction
elements
what kinds of solids can form crystals in which atoms lie only on the lattice points, so that the crystal structure and lattice points have identical patterns
1/8
what proportion of an atom at a corner of a unit cell is IN the unit cell
1/2
what proportion of an atom at a face of a unit cell is IN the unit cell
1/4
what proportion of an atom at an edge of a unit cell is IN the unit cell
ionic
what type(s) of metal(s) has/have charged particles throughout the solid
metallic
what type(s) of metal(s) has/have high mobility of electrons throughout the solid
covalent-network and ionic
what type(s) of solid(s) has/have high melting point and low electrical conductivity
metallic and molecular
what type(s) of solid(s) is/are soft and has/have relatively low melting point(s)
graphene is a single sheet of carbon atoms and graphite contains many, and larger, sheets of carbon atoms
whats the major difference between graphene and graphite
s, NOT d
when transition metals are oxidized, what subshell do they lose electrons from first
polymers
which is stronger and has a higher melting point? polymers or molecular solids
number of valence electrons and electronegativity
with metals, conductivity increases with
