Page 1
Lecture 2
Materials Science and
Engineering
Syllabus
International University
National University – HCMC
Dr. Nguyen Dinh Uyen
Page 2
Chapter 2
Atomic Structure and
Interatomic Bonding
Dr. Uyen Nguyen
Page 3

Problem 1:
A plane travels 2500 miles in 5 hours when it flies into the wind. When
the same plane flies with the wind, it can travel the same distance in 4
hours. Find the speed of the plane in still air and the speed of the wind

Problem 2:
Joe and Steve are saving money. Joe starts with $105 and saves
$5 per week. Steve starts with $5 and saves $15 per week. After
how many weeks do they have the same amount of money?
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Chapter Outline

Review of Atomic Structure
 Electrons,
protons, neutrons, quantum mechanics of atoms, electron states, the
periodic Table

• Atomic Bonding in Solids
 Bonding

energies and forces
• Primary Interatomic Bonding
 Ionic
 Covalent
 Metallic

• Secondary Bonding
 Three

types of dipole-dipole bonds
• Molecules and molecular solids
Page 5
Review of Atomic Structure

Structure of atoms:

Charges:
 Electrons
and protons have negative and positive charges
of the same magnitude, 1.6 × 10-19 Coulombs.
 Neutrons are electrically neutral.

Masses:
and Neutrons have the same mass, 1.67 × 10-27 kg.
 Mass of an electron is much smaller, 9.11 × 10-31 kg and
can be neglected in calculation of atomic mass.
 Protons

The atomic mass (A) = mass of protons + mass of
neutrons
 Protons
gives chemical identification of the element
 # protons = atomic number (Z)
 # neutrons defines isotope number
Page 6
Review of Atomic Structure

The atomic mass unit (amu)
 is
often used to express atomic weight. 1 amu is defined as 1/12 of the atomic
mass of the most common isotope of carbon atom that has 6 protons (Z=6) and six
neutrons (N=6).
 Mproton ≈ Mneutron = 1.66 x 10-24 g = 1 amu.
 The atomic mass of the 12C atom is 12 amu.

The atomic weight of an element
=
weighted average of the atomic masses of the atoms naturally occurring
isotopes. Atomic weight of carbon is 12.011 amu.
 The atomic weight is often specified in mass per mole.

A mole is the amount of matter that has a mass in grams equal to the atomic
mass in amu of the atoms (A mole of carbon has a mass of 12 grams).
number of atoms in a mole is called the Avogadro number, Nav = 6.023 × 1023.
 1 amu/atom = 1 gram/mol
 Example:
 The
 Atomic
weight of iron = 55.85 amu/atom = 55.85 g/mol
Page 7
Review of Atomic Structure

Simple Calculations:

The number of atoms per cm3, n, for material of density d (g/cm3) and atomic
mass M (g/mol): n = Nav × d / M

Example 1:
is the number of atoms per cm3 for Graphite (carbon): d = 2.3 g/cm3, M = 12
g/mol?
n = 6×1023 atoms/mol × 2.3 g/cm3 / 12 g/mol = 11.5 × 1022 atoms/cm3
 What is the number of molecules per cm3 for Water (H2O),d=1 g/cm3 , M = 18
g/mol
n = 6×1023 molecules/mol × 1 g/cm3 / 18 g/mol = 3.3 × 1022 molecules/cm3
 What

Example 2:
is the mean distance (L) between atoms for a material with n= 11.5 × 1022
atoms/cm3?
L = (1/n)1/3 = 0.205 nm
 What
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Use Matlab to solve the examples
Example 1:
What is the number of atoms per cm3 for
Graphite (carbon): d = 2.3 g/cm3, M = 12
g/mol?
n = 6×1023 atoms/mol × 2.3 g/cm3 / 12
g/mol = 11.5 × 1022 atoms/cm3
What is the number of molecules per cm3 for
Water (H2O) d = 1 g/cm3, M = 18 g/mol
n = 6×1023 molecules/mol × 1 g/cm3 / 18
g/mol = 3.3 × 1022 molecules/cm3
Example 2:
What is the mean distance (L) between atoms
for a material with n= 11.5 × 1022 atoms/cm3?
L = (1/n)1/3 = 0.205 nm
1.15x10^23 atoms
Hint in Matlab:
Na=6*10^23
3.3*10^22 molecules
2.05*10^-8 meter
Hint in Matlab:
n=11.5*10^22
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Bohr Atomic Model
Bohr model attempt to describe both
- Electron position in discrete orbital
- Electron energy (quantize energy)
Bohr Atomic Model
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Wave-Mechanical Model
Bohr Model
Discrete Orbital
Wave-Mechanical Model
Electron Cloud
Page 11

Quantum Numbers
 1-
Principal Quantum Number (Shell Designation)
 2- Subshells
 3- Number of States
 4- Spin Moments
Page 12
Page 13

Electron Configuration

Pauli Exclusion Principle: stipulates that each electron state can hold no
more than two electrons, which must have opposite spins.
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1s22s22p63s1
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Valence Bond
Outer most shell electrons
are called Valence electrons
When the outer most shell
are not filled with electrons,
these valence electrons
responsible for the bonding
with other atoms to form
atomic and molecular
structures
Note: Sometimes the outer most shell is
completely filled with electrons (Neon
(Ne), Argon (Ar), Krypton (Kr), they
become chemically unreactive.
Page 16
Periodic Table
Page 17
Atomic Bonding in Solid
Net force FN = FR + FA
Two types of Force
0 = FR + FA
FR
FA
Repulsive
Attractive
Equilibrium
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Energy
r
E N   FN dr

r
r


E N   FR dr   FA dr
 ER  E A
at equilibriu m we have E0
Each material has different types of bonds, therefore has different value of E0.
Note: The electron volt (eV) – energy unit convenient for
description of atomic bonding
1eV = q x V = 1.6x10-19 coulombs x 1 volts = 1.6x10-19 J
Page 19
Types of Primary Bond
Two
types of bonding
Primary
bonding
Ionic
Covalent
Metallic
Energy
100-1000 KJ/mol or 1-10 eV/atom
Secondary
bonding or
Van De Walls bonding
Fluctuating
Induced Dipole
Permanent dipole bonds
Polar molecule-induced dipole
bonds
< 100 KJ/mol or < 1 eV/atom
Page 20
Primary Bonding

Ionic Bonding: is typical for elements that are situated at the horizontal
extremities of the periodic table. Atoms from the left (metals) are ready to
give up their positively charge electrons (Cation) to the (non-metallic)
atoms from the right that accepts negatively charge electron (anion).
Example: combine Na and Cl
to create salt
https://www.youtube.com/watch?v=zpaHP
XVR8WU
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Primary Bonding

Covalent Bonding: electrons are shared between the molecules, to
saturate the valency. In this case the electrons are not transferred as in the
ionic bonding, but they are localized between the neighboring ions and form
directional bond between them.
Example: Methane CH4
Recall:
1st shell – s – max 2 electrons
2nd shell – s and p – max 6 electrons
https://www.youtube.com/watch?v=h24UmH38_LI
Page 22
Primary Bonding

Metallic Bonding: Valence electrons are detached from atoms, and spread
in an 'electron sea' that "glues" the positive ions together
Valence electrons are freely
moved into an ‘electron sea’ or
“electron cloud”.
The non-valence electron form
the inner ion cores.
https://www.youtube.com/watch?v=S08qdOTd0w0
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Secondary Bonding

Secondary = van der Waals = physical (as opposite to primary bonding that
involves e- transfer) bonding results from interaction of atomic or molecular
dipoles and is weak, ~0.1 eV/atom or ~10 kJ/mol.

Dipole: electric dipole exists whenever there is some separation of positive
and negative portions of an atom or molecule.
+
-
+
+
https://www.youtube.com/watch?v=HGc9RFD7iSE
-
-
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Types of Secondary Bonding

Fluctuating Induced Dipole Bonds

Polar Molecule-Induced Dipole Bonds

Permanent Dipole Bonds
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Bonding Energy and Melting Temperatures
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HW

Read Chapter 1

Read Chapter 2

Problems:

2.1

2.3

2.4

2.5

2.11

2.13 (use matlab)

2.15a (use matlab plot, r from 0.1 to 1nm, increment step of 0.01nm)

Note: the axis for the plot should be X(0,1), Y(-7,20))

2.15b (Use Matlab to determine Ro and Eo) Use Text command to
show the results on to the plot.
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2.15a (use matlab plot, r from 0.1 to 1nm,
increment step of 0.01nm)
Note: the axis for the plot should be X(0,1),
Y(-7,20))
2.15b (Use Matlab to determine Ro and
Eo) Use Text command to show the results
on to the plot.