l2 structure of matter_٠٤١١١٢.pdahmed and mouhmmed

طب بشري جامعة عدن كلية الطب
وهو معد من قبل الدكتور المتخصص في هذه المادة العلمية

1. STRUCTURE OF
MATTER
Prepared by :
Dr. Marwa.mohammed.Hassan

2. 1. Introduction.
2. Matter
3. Interatomic bonding
a). Primary bonding
Ionic
Covalen
Metallic
b). Secondary bonding
Hydrogen bonds
Vanderwaals forces
4. Interatomic bond distance & Bond energy.
5. Crystalline structure –Lattice types.

4. Matter
is that it is any substance which has mass and occupies
space.

6. Atom
Is a unit of matter, the smallest unit of an element, having
all the characteristics of that element and consisting of a
dense,central, positivelycharged nucleus surrounded by a
system of electrons.
An atom itself is made up of three kinds
of particles called subatomic particles;
1-Protons
2-Neutrons
3-Electrons

7. -Any material is composed of atoms and molecules.
The atoms consist :
of electrons, protons and neutrons.
The nucleus consist:
of protons (+ve) and neutrons (not charge) , the electron is
(-ve) charge.
Each element has a different number of electrons
surrounding its nucleus.
This number of electronic specific for each element and act
as identifying characteristic.

8. -Number of electrons must be = number of protons this
number called atomic number of element.
-The differenceof properties of the different atoms is due to
different numbers and arrangement of electronssurrounding
the nucleus of each atoms.

9. Stat of matter:
There is force of attraction between atoms that hold them
together.
In gasesthis force is minimaland the molecules of gases
have higher energy than liquids,

10. Inter atomic attraction:
In solids, atoms are held together by varietyof forces, these
forces are either primaryor secondary.
The importance in dentistry of knowledge of atomic
bonding is to explain the behavior of dental materials and
predict certain characteristicproperties of dental materials.

11. Interatomic attractions are associated with the electronic configuration
of atoms.
This configuration is obtained through one of the following means:
1. Receiving extra electrons to complete the outer shell electrons
( the atom becomes –veion)
2. Releasing electrons so that the outer shell has eight electrons (the
atoms becomes +veion)
3. Sharingelectrons so that the outer shell of two or more atoms are
complete.

12. Within the molecule, the atoms are held together by strong
intramolecular attractive force "interatomic bonds" while
the intermolecular bonds between molecules may be weak
and this known as secondary bonds.

14. I. Primary bonds:
I.1. IONIC BOND:
Formed by the transferof electron or electrons from one
atomto another. This causes an atoms to be positiveion it
looses electron then there mutual attraction between the v+
and v-ions.
•E.g.: Na
+
Cl
-
(one atom looses electron and another atom
received electron)

15. Characteristic properties of ionic bonds are:
1.Heat resistant
2.Insolublein organic solvents
3. Ready dissolved in ionizing solvents such as
water, acid and alkaline
4. Their solutions can conduct an electric
current.
5. Basic bond for glasses and ceramics.

16. I.2.COVALENT BOND:
It arises when atoms share their electrons
so that each electron shell achieves a
highly stable configuration.
E.g.: H2

17. Characteristic properties of covalent bonds are:
1. Highly direction bond .
2. Very strong and high resistance .
3. Insulators .
4. Water insoluble.
5. Basic bonds for polymer.

18. I.3. METALIC BOND:
Metallicbonding occurs when a large number of
metal atoms are present, which readily give up the
electrons in their valence shells.
Occursin metals, electron move freely around the
v+ ions giving electron cloud, attraction between
electron cloud and (v+)lycharged ion of metal
atoms

20. Characteristic of metallic bonds are:
1. High electricalconductivity.
2. High thermal conductivity.
3. Opaquebecause the free electrons may
absorb light.
4. It lead to crystallinearrangement in metals.

21. Arrangement of atoms:
The properties of materials depend on the type of
bonding, in the same type they depend on the
arrangement of their atoms.
Sucharrangementsinclude:
1-molecular structure.
2-crystal structure.
3-amorphous structure.

22. 2-According to arrangement of atoms:
a.Crystalline solid:
atoms are regularly arranged with repetition in three
dimensions (crystal lattice), definite melting point, low
internal energy.
b. Amorphous solid:
without form, have Tg ( glass temperature), high internal
energy.

23. Types of space lattice:
The simplest method of study the lattice
configurations is to consider a unit cell which is
the smallest repeating unit that is contained in a
crystal lattice.

24. 1-Cubic system:
The length of the axes a,b,care equal and
the interfacial angels equal 90
0
a.Simplecubic space lattice : unit cell
have one atoms at each corner
A.p= 8 x 18 = 1 atom.

25. b.Bodycentered cubic (BBC)
unit cell have one atom at each corner of the cubic and
another atom at the center of the unit cell

26. C. Face centered cubic (FCC).
Unit cell have one atom at each of the eigth
corners and one atom in the center of each of
the six faces.

27. 2. Tetragonal system
A = b ≠ c.
The interfacial angles are equal to 90
0
3. Hexagonal system:
A = b ≠ c.
The interfacial angles A=B=90, the angle c=
120

28. Polymorphism
Material have the same chemical composition but
found naturally in different physical form .
Can be changed by altering the surrounding physical
condition.

29. With application of heat two different forms of silica
there are 2 types of transformation can take place.
Displacive
transformation
Reconstructive
transformation
Reversible reactionIrreversible reaction
Occurs at specific t
0
-re
(low energy)
Need more or high
energy
Rapid transformationMore slowly
No breakage of bondsInvolve breakage of
bonds
Accompanied by
thermal expansion.
No thermal expansion
Change from α to βNo change from α to β

30. Thank you 