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LESSON 5 SOLIDS.pptx
1.
2. SOLIDS
The different
types of crystals:
ionic, covalent,
molecular, and
metallic are also
referred to as
“types of solids.”
3. What are the two general types of solids?
What features can be used to distinguish a
crystalline solid from an amorphous solid?
Solids can be
categorized into
two groups: the
crystalline solids
and the
amorphous solids.
4. 1. Arrangement of particles
The components of
a solid can be
arranged in two
general ways: they
can form a regular
repeating three-
dimensional
structure called a
crystal lattice.
5. 1. Arrangement of particles
The components of
a solid can be
arranged in two
general ways: they
can form a regular
repeating three-
dimensional
structure called a
crystal lattice for a
crystalline solid.
6. 1. Arrangement of particles
…or they can
aggregate with
no particular
long range
order, and
form an
amorphous
7. 1. Arrangement of particles
Crystalline solids are
arranged in fixed
geometric patterns or
lattices. Examples of
crystalline solids are ice
and sodium chloride
(NaCl), copper sulfate
(CuSO4), diamond,
graphite, and sugar
(C12H22O11). The ordered
arrangement of their units
maximizes the space they
occupy and are essentially
8. 1. Arrangement of particles
More than 90% of
naturally occurring and
artificially prepared
solids are crystalline.
Minerals, sand, clay,
limestone, metals, alloys,
carbon (diamond and
graphite), salts (e.g. NaCl
and MgSO4), all have
crystalline structures.
9. 1. Arrangement of particles
The repetition of
structural units of
the substance
over long atomic
distances is
referred to as
long-range order.
10. 1. Arrangement of particles
Amorphous solids have
a random orientation of
particles. Examples of
amorphous solids are
glass, plastic, coal, and
rubber. They are
considered super-cooled
liquids where molecules
are arranged in a
random manner similar
to the liquid state.
11. 1. Arrangement of particles
Amorphous solids
(e.g. glass), like
liquids, do not
have long range
order, but may
have a limited,
localized order in
their structures.
12. 2. Behavior when Heated
The presence or
absence of long-
range order in the
structure of solids
results in a
difference in the
behavior of the
solid when heated.
13. 2. Behavior when Heated
The surroundings of
particles in the
structure are
uniform, and the
attractive forces
experienced by the
particles are of
similar types and
strength.
14. 2. Behavior when Heated
These attractive
forces are broken
by the same
amount of energy,
and thus, crystals
become liquids at
a specific
temperature (i.e.
the melting point).
15. 2. Behavior when Heated
Amorphous solids soften
gradually when they are
heated. They tend to
melt over a wide range
of temperature. This
behavior is a result of
the variation in the
arrangement of particles
in their structures,
causing some parts of
the solid to melt ahead
of other parts.
16. FOUR TYPES OF CRYSTALS
The four types of
crystals differ in
the kind of
particles that
make up the
crystal and the
attractive forces
that hold these
particles together.
17. 1. METALLIC CRYSTAL
Metallic crystals are
made of atoms that
readily lose
electrons to form
positive ions
(cations), but no
atoms in the crystal
would readily gain
electrons.
18. 1. METALLIC CRYSTAL
The crystal is held
together by
electrostatic
interactions between
the cations and
delocalized electron.
These interactions are
called metallic bonds.
This model of metallic
bonding is called the
“sea of electrons”
model.
20. 1I. IONIC CRYSTAL
These are made of
ions (cations and
anions). These
ions form strong
electrostatic
interactions that
hold the crystal
lattice together.
21. 1I. IONIC CRYSTAL
The electrostatic
attractions are
numerous and extend
throughout the
crystal since each ion
is surrounded by
several ions of
opposite charge,
making ionic crystals
hard and of high
melting points.
22. 1I. IONIC CRYSTAL
Ionic substances can
conduct electricity in
the liquid or molten
state or when
dissolved in water,
indicating that in
these states, charged
particles are able to
move and carry
electricity.
23. 1I. IONIC CRYSTAL
However, the solid
state is generally
nonconducting
since the ions are in
fixed positions in
the crystal lattice
and are unable to
move from one
point to another.
24. 1I. IONIC CRYSTAL
Ionic crystals are brittle and would shatter into
small pieces when deformed or when pressure is
applied on the crystal. The shifting of ions cause
repulsions between particles of like charges.
26. 1II. MOLECULAR CRYSTAL
Molecular crystals
are made of
atoms, such as in
noble gases, or
molecules, such as
in sugar,
C12H22O11, iodine,
I2, and
naphthalene,
27. 1II. MOLECULAR CRYSTAL
The atoms or molecules
are held together by a
mix of hydrogen
bonding/ dipole-dipole
and dispersion forces,
and these are the
attractive forces that are
broken when the crystal
melts. Hence, most
molecular crystals have
relatively low melting
points.
28. 1II. MOLECULAR CRYSTAL
The valence
electrons of
molecular
substances are used
in bonding and
cannot move about
the crystal structure.
Hence, the crystals
are nonconducting.
29. 1II. MOLECULAR CRYSTAL
The absence of any mobile
particles make molecular
crystals unable to transmit
heat fast. The crystals are
brittle because the
attractive forces that hold
the molecules in the crystal
are highly directional and a
shift in positions of the
molecules would break
them.
31. 1V. COVALENT NETWORK CRYSTAL
Examples of
these are
diamonds and
silicon dioxide.
What are the
properties of
CNCs?
32. IV. COVALENT NETWORK CRYSTAL
Covalent network
crystals are made of
atoms in which each
atom is covalently
bonded to its nearest
neighbors. The atoms
can be made of one type
of atom (e.g. Cdiamond and
Cgraphite) or can be made
of different atoms (e.g.
SiO2 and BN)
33. IV. COVALENT NETWORK CRYSTAL
In a network solid, there
are no individual molecules
and the entire crystal may
be considered one very
large molecule. Formulas
for network solids, like
those for ionic compounds,
are simple ratios of the
component atoms
represented by a formula
unit.
34. IV. COVALENT NETWORK CRYSTAL
The valence electrons
of the atoms in the
crystal are all used to
form covalent bonds.
Because there are no
delocalized electrons,
covalent network
solids do not conduct
electricity.
35. IV. COVALENT NETWORK CRYSTAL
Rearranging or breaking
of covalent bonds
requires large amounts
of energy; therefore,
covalent network solids
have high melting
points. Covalent bonds
are extremely strong, so
covalent network solids
are very hard.
High melting point – a large amount of energy is needed to melt the crystal since the forces of attraction to be broken are numerous and extend throughout the crystal. • Dense – atoms are packed closely together. Metals exhibit close-packing structures, a most economical way by which atoms utilize space. • Electrical conductivity – then delocalized electrons move throughout the crystal. • Thermal or heat conductor – the delocalized electrons collide with each other as they move through the crystal, and it is through these collisions that kinetic energy is transferred . • Malleability/ductility – when stress is applied to the metal, the metal cations shift in position, but the mobile electrons simply follow the movement of the cations. The attractive forces between cations and mobile electrons are not broken.
Luster – the motion and collisions of electrons allow it to gain and lose energy, some of these in the form of emitted light that is observed as luster.
