材料科学基础(清华大学)(1)_OK
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材料科学基础
Fundamental of Materials
Prof: Tian Min Bo
Tel: 62795426 ，62772851 E-mail: tmb@ Department of Material Science and Engineering Tsinghua University. Beijing 100084
H
H
18
2. Secondary bonding
Fluctuating Dipole bonds These bonding forces arise because the asymmetrical
distribution of electron charge distribution in these atoms creates electric dipoles.
19
Permanent Dipole bonds
Permanent Dipole bonds exist between adjacent polar molecules.
105
Hydrogen
bonding
20
3. Mixed bonding Ionic-Covalent Mixed bonding
12
• Ⅲ.Secondary bonding （Van Der waals bonding)
The driving force for secondary bonding is the attract ion of the electric dipoles contained in atoms or molecu les.
An electric dipole moment is created when two equal and opposite charges are separated.
Neutral atom
E
13
Van Der waals bonding
14
A dipole moment is defined as the charge value multiplied by the separation distance between positive and negative charges, or
6
7
Interionic Forces
Fat
t
ract iv e
Z1Z2e2
4 0 a 2
Frepulsive
nb a n1
Fnet
Z1Z2e2
4 0 a 2
nb a n1
Z1, Z2＝number of electrons removed or added from the
atoms during the ion formation
uced in atoms or molecules, we refer to them as London forces.
16
forces
When an induced dipole interacts with a molecule that has a permanent dipole moment, we refer to this interaction as a Debye interaction.
Lesson two
§1.2 Atomic bonding
Ⅰ.Bonding forces and energies
FN FA FR
FN : net force FA : attractive force FR : repulsive force
2
3
Bonding energies:
E Fdr
e ＝electron charge a ＝interionic separation distance
8
ε0＝permittivity of free space＝8.85×10-12C2/(N·m2)
Interionic Energies
Enet
Z1Z 2e 2
4 0 a
b an
Attractive energy
11
3. Metallic bonding Metallic bonding occurs in solid metals. In metals in solid state, atoms are packed relatively cl
ose together in a systematic pattern or crystal structure.
qd
dipole moment
q magnitude of electric charge d separation distance between the charge centers
15
1. Van der waals interactions
London forces If the interactions are between two dipoles that are ind
Repulsive energy
9
Example problem 2.1
If the attractive force between a pair of Mg2+and S2- is 1.49×108N and if the S2- ion has a radius of 0.184nm, calculate a value for the ionic radius of the Mg2+ ion in nanometers.
21
Summary
Primary atomic bonds
Ionic bonding Covalent bonding Metallic bonding
Secondary atomic bonds
Permanent dipole bonds Fluctuating dipole bonds
22
Examples and Discussions
H
oxygen
H
17
Keesom forces
If the interactions are between molecules that are permanently polarized, we refer to these as Keesom interaction.
H oxygen
H
oxygen
For atomic systems:
EN EA ER
4
5
• Ⅱ.Primary interatomic bonds
1. Ionic bonding Ionic bonding is always found in compounds that are composed of both metallic and nonmetallic elements, elements that are situated at the horizontal extremities of the periodic table.
Solution
Fat
t
ract iv e
Z1Z2e2
4 0 a 2
a0
Z1Z2e2
4 0 Fat t ract iv e
0.249nm
(2)(2)(1.601019C)2
4[8.851012 C2 (N m2）](1.49108 N)
又a0
rMg2
r
S
2
10
rMg2
a0
r
S
2
0.249nm
23
Exercise
24
Thank you !
225
0.184nm
0.065nm
2. Covalent bonding Materials with covalent bonding are characterized by
bonds that are formed by sharing of valence electrons a mong two or more atoms.
% ionic character (1 e(1/ 4)(XA XB)2 )(100%)
XA and XB are the electronegativities of the atoms A
and B in the compound
Metallic-Covalent Mixed Bonding Metallic-Ionic Mixed Bonding
Fundamental of Materials
Prof: Tian Min Bo
Tel: 62795426 ，62772851 E-mail: tmb@ Department of Material Science and Engineering Tsinghua University. Beijing 100084
H
H
18
2. Secondary bonding
Fluctuating Dipole bonds These bonding forces arise because the asymmetrical
distribution of electron charge distribution in these atoms creates electric dipoles.
19
Permanent Dipole bonds
Permanent Dipole bonds exist between adjacent polar molecules.
105
Hydrogen
bonding
20
3. Mixed bonding Ionic-Covalent Mixed bonding
12
• Ⅲ.Secondary bonding （Van Der waals bonding)
The driving force for secondary bonding is the attract ion of the electric dipoles contained in atoms or molecu les.
An electric dipole moment is created when two equal and opposite charges are separated.
Neutral atom
E
13
Van Der waals bonding
14
A dipole moment is defined as the charge value multiplied by the separation distance between positive and negative charges, or
6
7
Interionic Forces
Fat
t
ract iv e
Z1Z2e2
4 0 a 2
Frepulsive
nb a n1
Fnet
Z1Z2e2
4 0 a 2
nb a n1
Z1, Z2＝number of electrons removed or added from the
atoms during the ion formation
uced in atoms or molecules, we refer to them as London forces.
16
forces
When an induced dipole interacts with a molecule that has a permanent dipole moment, we refer to this interaction as a Debye interaction.
Lesson two
§1.2 Atomic bonding
Ⅰ.Bonding forces and energies
FN FA FR
FN : net force FA : attractive force FR : repulsive force
2
3
Bonding energies:
E Fdr
e ＝electron charge a ＝interionic separation distance
8
ε0＝permittivity of free space＝8.85×10-12C2/(N·m2)
Interionic Energies
Enet
Z1Z 2e 2
4 0 a
b an
Attractive energy
11
3. Metallic bonding Metallic bonding occurs in solid metals. In metals in solid state, atoms are packed relatively cl
ose together in a systematic pattern or crystal structure.
qd
dipole moment
q magnitude of electric charge d separation distance between the charge centers
15
1. Van der waals interactions
London forces If the interactions are between two dipoles that are ind
Repulsive energy
9
Example problem 2.1
If the attractive force between a pair of Mg2+and S2- is 1.49×108N and if the S2- ion has a radius of 0.184nm, calculate a value for the ionic radius of the Mg2+ ion in nanometers.
21
Summary
Primary atomic bonds
Ionic bonding Covalent bonding Metallic bonding
Secondary atomic bonds
Permanent dipole bonds Fluctuating dipole bonds
22
Examples and Discussions
H
oxygen
H
17
Keesom forces
If the interactions are between molecules that are permanently polarized, we refer to these as Keesom interaction.
H oxygen
H
oxygen
For atomic systems:
EN EA ER
4
5
• Ⅱ.Primary interatomic bonds
1. Ionic bonding Ionic bonding is always found in compounds that are composed of both metallic and nonmetallic elements, elements that are situated at the horizontal extremities of the periodic table.
Solution
Fat
t
ract iv e
Z1Z2e2
4 0 a 2
a0
Z1Z2e2
4 0 Fat t ract iv e
0.249nm
(2)(2)(1.601019C)2
4[8.851012 C2 (N m2）](1.49108 N)
又a0
rMg2
r
S
2
10
rMg2
a0
r
S
2
0.249nm
23
Exercise
24
Thank you !
225
0.184nm
0.065nm
2. Covalent bonding Materials with covalent bonding are characterized by
bonds that are formed by sharing of valence electrons a mong two or more atoms.
% ionic character (1 e(1/ 4)(XA XB)2 )(100%)
XA and XB are the electronegativities of the atoms A
and B in the compound
Metallic-Covalent Mixed Bonding Metallic-Ionic Mixed Bonding