CHAPTER 2
SOLID-STATE CHEMISTRY
Of the three states of matter, solids possess the most structural diversity. Whereas
gases and liquids consist of discrete molecules that are randomly distributed due to
thermal motion, solids consist of molecules, atoms, or ions that are statically
positioned. To fully understand the properties of solid materials, one must have a
thorough knowledge of the structural interactions between the subunit atoms, ions,
and molecules. This chapter will outline the various types of solids, including
structural classifications and nomenclature for both crystalline and amorphous
solids. The material in this key chapter will set the groundwork for the rest of this
textbook, which describes a variety of materials classes.
2.1. AMORPHOUS VS. CRYSTALLINE SOLIDS
A solid is a material that retains both its shape and volume over time. If a solid
possesses long range, regularly repeating units, it is classified as a crystalline
material. Crystalline solids are only produced when the atoms, ions, or molecules
have an opportunity to organize themselves into regular arrangements, or lattices.
For example, crystalline minerals found in nature have been formed through many
years of extreme temperature and pressure, or slow evaporation processes. Most
naturally occurring crystalline solids comprise an agglomeration of individual
The Essay on Cold Solid Hot Material Heat
First, you need to know what heat is. Heat is the rattling, wiggling motion of all the atoms that make up a substance. It's a form of motion energy, but special because the solid as a whole isn't going anywhere. How is that possible? Imagine a large crowd of people standing around, in line, perhaps, for concert tickets. They could be standing quietly or shoving and milling about, even though the ...
microcrystalline units; single crystals without significant defects are extremely
rare in nature, and require special growth techniques (see p. 28).
If there is no long-range structural order throughout the solid, the material is
best described as amorphous. Quite often, these materials possess considerable
short-range order over distances of 1–10 nm or so. However, the lack of long-
range translational order (periodicity) separates this class of materials from their
crystalline counterparts. Since the majority of studies have been addressed to
study crystalline solids relative to their amorphous counterparts, there is a common
misconception that most solids are crystalline in nature. In fact, a solid product
generated from many chemical reactions will be amorphous by default, unless special
procedures are used to facilitate molecular ordering (i.e., crystal formation).
Although the crystalline state is more thermodynamically-favorable than the
13
2 Solid-State Chemistry
14
Table 2.1. Glass Transition Temperatures
Tg( C)
Material
Intermolecular bonding
SiO2
Covalent
1,430
Borosilicate glass
Covalent
550
Pd0.4Ni0.4P0.2
Metallic
580
BeF2
Ionic
570
As2S3
Covalent
470
Polystyrene
Van der Waal
370
Se1
Covalent
310
Poly(vinyl chloride)
Van der Waal
81
À30
Polyethylene
Van der Waal
disordered state, the formation of amorphous materials is favored in kinetically
bound processes (e.g., chemical vapor deposition, sol-gel, solid precipitation, etc.).[1]
Some materials featuring extended networks of molecules such as glasses may
never exist in the crystalline state. In these solids, the molecules are so entangled or
structurally complex that crystallization may not occur as the temperature is slowly
decreased. Due to the rigidity of the solid, but proclivity to remain in the amorphous
state, these compounds have been incorrectly referred to as supercooled liquids.
It was even thought that a slow flow of glass over hundreds of years has caused
The Review on The Use of Waste Glass as Construction Material
Introduction Waste glass is of great concern in some developed countries, particularly in the urban areas. This is because of the amount of waste material generated from both municipal and construction sources, and the lack of waste disposal areas to receive the material. Countries like Japan, the United States of America, and Australia have taken the initiative to invest in the recycling of glass ...
nineteenth century stained glass windows to have a proportionately thicker base.[2]
However, it is now well understood that the glass structure remains in tact unless
its threshold transition temperature is exceeded. This parameter is known as the
glass transition temperature, Tg, and corresponds to the temperature below which
molecules have very little mobility.
Other amorphous solids such as polymers, being rigid and brittle below Tg,
and elastic above it, also exhibit this behavior. Table 2.1 lists the glass transition
temperatures of common solid materials. It should also be noted that whereas
crystalline solids exhibit a discrete melting point, amorphous solids undergo a
solid–liquid phase transition over a range of temperatures. Although most solid-
state textbooks deal almost exclusively with crystalline materials, this text will
attempt to address both the crystalline and amorphous states, describing the
structure/property relationships of major amorphous classes such as polymers
and glasses.
2.2. TYPES OF BONDING IN SOLIDS
Every amorphous and crystalline solid possesses certain types of inter- and intramo-
lecular interactions between its subunits that govern its overall properties. Depend-
ing on the nature and strength of these interactions, a variety of physical, optical, and
electronic properties are observed. For example, intramolecular forces (i.e., atomic
separations/inter-atomic bonding energies) directly influence the conductivity,
thermal expansion, and elasticity of a material; in contrast, intermolecular forces
will govern the melting/boiling/sublimation point, solubility, and vapor pressure of a
2.2. Types of Bonding in Solids
15
material. As expected, these associations not only govern the behavior of a material
in the solid state, but also for the less ordered liquid phase. For example, the
hydrogen bonding interactions between neighboring water molecules within an ice
lattice are also important in the liquid phase, resulting in high surface tension and
The Essay on Mass Spectrometer Water Ions Charged
Mass Spectrometer A mass spectrometer produces charged particles (ions) from the chemical substances that are to be analyzed. The mass spectrometer then uses electric and magnetic fields to measure the mass (weight) of the charged particles. There are many different kinds of mass spectrometers, but all use magnetic and / or electric fields to exert forces on the charged particles produced from the ...
finite viscosity. For the gaseous state, intermolecular forces have been overcome,
and no longer have an impact on its properties.
2.2.1. Ionic Solids
These solids are characterized by cationic and anionic species that are associated
through electrostatic interactions. All predominantly ionic salts possess crystalline
structures, as exhibited by common Group 1–17 or 2–17 binary salts such as NaCl
and CaCl2 (Figure 2.1).
The melting points of these solids are extremely high, as
very strong electrostatic attractions between counterions must be overcome.
Although oppositely charged ions have attractive interactions, like charges repel
one another. In the determination of the lattice energy, U, the sizes and charges of
the ions are most important (Eq. 1).
That is, the lattice energy for MgO would be
much greater than BaO, since the ionic bonding is much stronger for the magnesium
salt due to its high charge/small size (large charge density).
By contrast, the salt
MgN does not exist, even though Mg3þ and N3À would be very strongly attracted
through electrostatic interactions. The ionization energy required to produce the
trivalent magnesium ion is too prohibitive.
Figure 2.1. Ionic model for sodium chloride. This is a face-centered arrangement of chloride ions (white),
with sodium ions occupying the octahedral interstitial sites (red).
The attractive electrostatic forces, a,
between adjacent Na+ and ClÀ ions, and repulsive forces, r, between Na+ ions are indicated.
2 Solid-State Chemistry
16
NMZcation Zanion e2
n
ð1Þ
1À
U=
ro
ro
4peo
where: N ¼ Avagadro’s number (6.02 Â 1023 molecules molÀ1)
Zcation, anion ¼ magnitude of ionic charges;
r0 ¼ average ionic bond length
e ¼ electronic charge (1.602 Â 10À19 C)
4pe0 ¼ permittivity of a vacuum (1.11 Â 10À10 C2 JÀ1 mÀ1)
M ¼ the Madelung constant (see text)
n ¼ the Born exponent; related to the corresponding closed-shell electronic
The Essay on Metal Ion App Peptide Age
Alzheimer's Disease (AD), which is clinically characterized by a gradual deterioration of cognitive function, is the most common form of dementia (Brook meyer et al. 1998). It affects approximately 7-10% of individuals over the age of 65, and as many as 40% of individuals over the age of 80. These demographics are expected to grow, as average life expectancy continues to increase, and a growing ...
configurations of the cations and anions (e.g., [He] ¼ 5; [Ne] ¼ 7; [Ar] or
[3d10][Ar] ¼ 9; [Kr] or [4d10][Kr] ¼ 10; [Xe] or [5d10][Xe] ¼ 12)
It is noteworthy that the calculated lattice energy is quite often smaller than
the empirical value. Whereas the ions in purely ionic compounds may be accurately
treated as hard spheres in the calculation, there is often a degree of covalency in
the bonding motif. In particular, Fajans’ rules describe the degree of covalency as
being related to the charge density of the cation and the polarizability of the anion.
In general, polarizability increases down a Periodic Group due to lower electrone-
gativities, and valence electrons being housed in more diffuse orbitals thus experien-
cing a much less effective nuclear charge. To wit, a compound such as LiI would
exhibit a significant degree of covalent bonding due to the strong polarizing potential
of the very small cation, and high polarizability of iodide. This is reflected in its lower
melting point (459 C) relative to a more purely ionic analogue, LiF (m.p. ¼ 848 C).
The Madelung constant appearing in Eq. 1 is related to the specific arrangement of
ions in the crystal lattice. The Madelung constant may be considered as a decreasing
series, which takes into account the repulsions among ions of similar charge, as well
as attractions among oppositely charged ions. For example, in the NaCl lattice
illustrated in Figure 2.1, each sodium or chloride ion is surrounded by six ions of
opposite charge, which corresponds to a large attractive force. However, farther
away there are 12 ions of the same charge that results in a weaker repulsive
interaction. As one considers all ions throughout the infinite crystal lattice, the
number of possible interactions will increase exponentially, but the magnitudes of
these forces diminishes to zero.
Ionic solids are only soluble in extremely polar solvents, due to dipole–dipole
interactions between component ions and the solvent. Since the lattice energy of the
crystal must be overcome in this process, the solvation of the ions (i.e., formation of
[(H2O)nNa]þ) represents a significant exothermic process that is the driving force for
The Essay on Transition Metals Electron Configuration
Name Symbol Electron Configuration Scandium S Titanium TVanadiuChromium C Manganese MIron F Cobalt C Nickel Copper C 10 4 s 1 Zinc Z 10 4 s 2 As Chromium and Copper are in the fourth period we would expect it to follow the same pattern as the other elements in the same periods as in the 4 s sub shell is filled first rather than the 3 d sub shell. Chromium (Cr) Expected Electronic ...
this to occur.
2.2.2. Metallic Solids
Metallic solids are characterized by physical properties such as high thermal and
electrical conductivities, malleability, and ductility (i.e., able to be drawn into a thin
wire).
Chemically, metals tend to have low ionization energies that often result in
2.2. Types of Bonding in Solids
17
metals being easily oxidized by the surrounding environmental conditions.
This explains why metals are found in nature as complex geological formations of
oxides, sulfates, silicates, aluminates, etc. It should be noted that metals or alloys
may also exist as liquids. Mercury represents the only example of a pure metal
that exists as a liquid at STP. The liquid state of Hg is a consequence of the
electronic configurations of its individual atoms. The 6s valence electrons are
shielded from the nuclear charge by a filled shell of 4f electrons. This shielding
causes the effective nuclear charge (Zeff) to be higher for these electrons,
resulting in less sharing/delocalization of valence electrons relative to other
metals. Further, relativistic contraction of the 6s orbital causes these electrons to
be situated closer to the nucleus, making them less available to share with neighbor-
ing Hg atoms.[3] In fact, mercury is the only metal that does not form diatomic
molecules in the gas phase. Energetically, the individual atoms do not pack into a
solid lattice since the lattice energy does not compensate for the energy required to
remove electrons from the valence shell.
Metallic bonding
The most simplistic model for the bonding in metallic solids is best described via the
free electron model. This considers the solid as a close-packed array of atoms, with
valence electrons completely delocalized throughout the extended structure. Since
the delocalization of electrons occurs more readily for valence electrons farther from
the nucleus (experiencing a lesser Zeff), metallic character increases going down a
Group of the Periodic Table. Perhaps the best example of this phenomenon is
The Essay on The Periodic Table Valence Electron
... valence electrons. When they combine with of atoms, they lose either 1 or both of their valence electrons. The compounds of transition metals ... include electron arrangement, reactivity, atomic size, and metallic properties. The valence number ... electrons. When you look at the dividing line between metals and nonmetal you see the metalloids. Metalloid means metal like. All metalloids are solid ...
observed for the Group 14 congeners. As you move from carbon to lead, the
elemental properties vary from insulating to metallic, through a transitional range
of semiconducting behavior for Si and Ge.
The close chemical association among neighboring metal atoms in the solid
gives rise to physical properties such as high melting points and malleability. The
nondirectional bonding in metals allows for two modes of deformation to occur
when a metal is bent. Either the atomic spacing between neighboring metal atoms in
the crystal lattice may change (elastic deformation), or planes of metal atoms may
slide past one another (plastic deformation).
Whereas elastic deformation results in a
material with “positional memory” (e.g., springs), plastic deformation results in a
material that stays malformed. We will consider the bonding modes of metals and
non-metals in more detail later in this chapter.
Although metals are mostly characterized by crystalline structures, amorphous
alloys may also be produced, known as metallic glasses. A recent example of such a
material is the multicomponent alloy Zr41Ti14Ni12Cu10Be23.[4] These materials
combine properties of both plastics and metals, and are currently used within electric
transformers, armor-piercing projectiles, and even sports equipment. The media
has recently been focused on this latter application, for LiquidMetal™ golf clubs,
tennis racquets, and baseball bats. Unlike window glass, metallic glass is not brittle.
Many traditional metals are relatively easy to deform, or bend permanently out of
