Solid State Chemistry: Principles and Classification of Solids
Solid state Chemistry
(CHEM 422)
Prof. Ayman Nafady
King Saud University
Chemistry Department
Week 1-2: Lectures
Solid State Chemistry
•
It is an in-depth examination of the
principles
and
concepts
underlying
the
synthesis
,
structure
,
bonding
,
reactivity
, and
physical properties
of
solid state materials.
2
3
4
5
•
Solid is a physical state of matter which is characterized by strong intermolecular
force of attraction and least intermolecular distance.
•
The constituent particles are held together with strong forces which make this
physical state compact and non-compressible.
•
The constituent particles of solids cannot move from their position but can vibrate at
their mean position.
•
They are held together with strong intermolecular forces such as ionic or strong
covalent bonding.
•
Because of these strong forces, they have definite shapes and volumes.
On the basis of ordered arrangement of particles, solids can be classified as
crystalline
and
amorphous
solid.
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l
i
d
S
t
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Crystalline solids
•
Crystalline solids are classified according to their properties and
structure into four Categories. These include:
•
(1) Ionic solids
•
(2) Molecular solids
•
(3) Metallic solids
•
(4) Covalent solids
(1)-Ionic Solids
•
Ionic solids:
are made of
ions
which sit in a
3
D
network
of positive and negative ions.
•
Are
very hard
but can be cleaved
Ionic solids properties
•
Do not conduct electricity
(no free ions or electrons)
except
when molten or aqueous (as ions are free to
move)
•
High melting point and boiling point
•
because of
very strong inter-particular attractions
(electrostatic attractions)
Soluble in polar substances
Polar solvents overcome the
electrostatic forces between ions
(2)-Molecular solids
•
Molecular solids are made of molecules.
•
There are strong bonds within the molecules
(
strong intra-molecular forces
)
•
but weak attractions between the molecules
•
(
weak inter – molecular forces
)
•
Properties of Molecular solids:
•
Have
low melting and boiling points
because of weak inter-molecular forces
The molecules themselves are not broken up – just moved apart from
each other when molten
Molecular solids properties cont’d
•
Do not conduct electricity
- even when molten
(no free ions or electrons)
•
Insoluble in water
and other polar substances
•
Few are solid at room temperature – eg. Dry
ice
Polar and non- polar particles
•
Molecular solids can be made from polar or non polar molecules.
•
The inter- molecular forces between
non-polar
molecules are
only
weak van der Waals forces.
•
Van der Waals attractions are the
weak electrostatic attractions
between atoms of different EN
•
Polar molecules have dipoles and so have
slightly stronger
attractions
between them meaning that the
melting point of a polar
molecular solid is a little higher
because more energy is needed to
overcome the slightly stronger forces.
(3)- Metallic solids
•
Metals are made of
positive nuclei held together by a sea of de-
localised electrons
(e
-
do not belong to any one nucleus)
•
Forces between the particles are
strong metallic bonds
•
Malleable
•
It can be hammered or bent into
different shapes without breaking
•
Ductile
T
hey can be drawn or pulled
into a long strand of wire without breaking
due to
non-directional metallic bonds
•
Atoms can slide over each other
Properties of metallic solids
•
Good conductors of heat
and electricity
due to
density and mobile electrons
can transmit energy quickly
•
High melting and boiling
points
due to strong metallic
bonds
•
Not soluble in any solvent
•
The strength of metallic
bonds varies and so
consequently the melting
and boiling points of
different metals varies.
4- Network solids
1.
1-D sloids (Linear chains)
are infinitely long linear chains held together by van der Waals
•
Properties:
•
Low MP but longer chains have higher MP than shorter
ones
•
Do no conduct electricity
•
Soft and flexible
•
Eg. Polythene, rubber, plastics
•
Made up of atoms connected by covalent bonds
•
The intermolecular forces are covalent bonds as well.
•
Characterized as being very hard with very high melting points and being poor conductors.
•
2. 2-D Layers
held together by weak van der Waals forces.
•
Graphite
is made of
layers of covalently bonded C atoms
.
•
The layers are
held together by weak van
der Waals forces
and have
delocalised
•
electrons
between them.
*this is very
•
unusual and graphite is the
only
non-
•
metal to conduct electricity
Properties of Graphite
•
Conducts electricity
because of delocalised
electrons
•
High melting point
– C atoms are held by strong
covalent bonds
•
Soft and greasy texture
(used as a lubricant) as the
layers slide past each-other easily – weak van der
Waals forces.
Graphite has only 2-D hexagonal
structure and therefore is not hard
like diamond.
•
3. 3-D covalent network solids
are made of
atoms
held together by
strong covalent bonds.
Diamond and silica (silicon dioxide) are two examples of
covalent network solids.
•
Diamond is the strongest substance known to man.
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Irregular shape
22
Amorphous Solids
•
Properties
•
No definite melting point
- no crystal lattice to break
•
Exhibit characteristic
glass transition temperature
,
Tg
•
Flow when subject to pressure over time
•
Isotropic i.e. same properties in all direction
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Solid State Chemistry (CHEM 422) explores the principles and concepts governing the synthesis, structure, bonding, reactivity, and properties of solid state materials. The course delves into crystalline vs. amorphous solids, highlighting categories like ionic, molecular, metallic, and covalent solids. Specifically, it breaks down the characteristics, properties, and structures of ionic and molecular solids, emphasizing factors like conductivity, melting points, solubility, and bonding types.
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Presentation Transcript
Solid state Chemistry (CHEM 422) Prof. Ayman Nafady King Saud University Chemistry Department
Week 1-2: Lectures Solid State Chemistry It is an in-depth examination of the principles and concepts underlying the synthesis, structure, bonding, reactivity, and physical properties of solid state materials. 2
Solid State Solid is a physical state of matter which is characterized by strong intermolecular force of attraction and least intermolecular distance. The constituent particles are held together with strong forces which make this physical state compact and non-compressible. The constituent particles of solids cannot move from their position but can vibrate at their mean position. They are held together with strong intermolecular forces such as ionic or strong covalent bonding. Because of these strong forces, they have definite shapes and volumes. On the basis of ordered arrangement of particles, solids can be classified as crystalline and amorphous solid. 5
Crystalline solids Crystalline solids are classified according to their properties and structure into four Categories. These include: (1) Ionic solids (2) Molecular solids (3) Metallic solids (4) Covalent solids
(1)-Ionic Solids Ionic solids: are made of ions which sit in a 3D network of positive and negative ions. Are very hard but can be cleaved
Ionic solids properties Do not conduct electricity (no free ions or electrons) except when molten or aqueous (as ions are free to move) High melting point and boiling point because of very strong inter-particular attractions (electrostatic attractions) Soluble in polar substances Polar solvents overcome the electrostatic forces between ions
(2)-Molecular solids Molecular solids are made of molecules. There are strong bonds within the molecules (strong intra-molecular forces) but weak attractions between the molecules (weak inter molecular forces) Properties of Molecular solids: Have low melting and boiling points because of weak inter-molecular forces The molecules themselves are not broken up just moved apart from each other when molten
Molecular solids properties contd Do not conduct electricity - even when molten (no free ions or electrons) Insoluble in water and other polar substances Few are solid at room temperature eg. Dry ice
Polar and non- polar particles Molecular solids can be made from polar or non polar molecules. The inter- molecular forces between non-polar molecules are only weak van der Waals forces. Van der Waals attractions are the weak electrostatic attractions between atoms of different EN Polar molecules have dipoles and so have slightly stronger attractions between them meaning that the melting point of a polar molecular solid is a little higher because more energy is needed to overcome the slightly stronger forces.
(3)- Metallic solids Metals are made of positive nuclei held together by a sea of de- localised electrons (e- do not belong to any one nucleus) Forces between the particles are strong metallic bonds Malleable It can be hammered or bent into different shapes without breaking Ductile They can be drawn or pulled into a long strand of wire without breaking due to non-directional metallic bonds Atoms can slide over each other
Properties of metallic solids Good conductors of heat and electricity density and mobile electrons can transmit energy quickly High melting and boiling points due to strong metallic bonds Not soluble in any solvent The strength of metallic bonds varies consequently the melting and boiling different metals varies. due to and so points of
4- Network solids Made up of atoms connected by covalent bonds The intermolecular forces are covalent bonds as well. Characterized as being very hard with very high melting points and being poor conductors. 1. are infinitely long linear chains held together by van der Waals Properties: Low MP but longer chains have higher MP than shorter ones Do no conduct electricity Soft and flexible Eg. Polythene, rubber, plastics 1-D sloids (Linear chains)
2. 2-D Layers held together by weak van der Waals forces. Graphite is made of layers of covalently bonded C atoms. The layers are held together by weak van der Waals forces and have delocalised electrons between them. *this is very unusual and graphite is the only non- metal to conduct electricity
Properties of Graphite Conducts electricity because of delocalised electrons High melting point C atoms are held by strong covalent bonds Soft and greasy texture (used as a lubricant) as the layers slide past each-other easily weak van der Waals forces. Graphite has only 2-D hexagonal structure and therefore is not hard like diamond.
3. 3-D covalent network solids are made of atoms held together by strong covalent bonds. Diamond and silica (silicon dioxide) are two examples of covalent network solids. Diamond is the strongest substance known to man.
Amorphous Solids Properties No definite melting point - no crystal lattice to break Exhibit characteristic glass transition temperature, Tg Flow when subject to pressure over time Isotropic i.e. same properties in all direction 22
