This document provides an overview of atomic bonding and properties. It discusses how the arrangement of atoms and interactions between atoms determine properties. The main types of bonds - ionic, covalent, and metallic - are introduced along with how they relate to properties like melting temperature and thermal expansion. Bonding concepts like bond energy, bond length, and the relationship between bonding strength and properties are explained through diagrams of bonding curves. The roles of factors like atomic radius, electronegativity, and bond type in determining properties are also summarized.
CONDUCTIVITY-TYPES-VARIATION WITH DILUTION-KOHLRAUSCH LAW - TRANSFERENCE NUMBER -DETERMINATION - IONIC MOBILITY - APPLICATION OF CONDUCTANCE MEASUREMENTS - CONDUCTOMENTRIC TITRATION
CONDUCTIVITY-TYPES-VARIATION WITH DILUTION-KOHLRAUSCH LAW - TRANSFERENCE NUMBER -DETERMINATION - IONIC MOBILITY - APPLICATION OF CONDUCTANCE MEASUREMENTS - CONDUCTOMENTRIC TITRATION
content-
Chemistry & Chemical Engineering
History of Catalysis
Catalysis
Recent trends in Catalysis
Future trends in Catalysis
Summary
role-
24% of GDP from Products made using catalysts (Food, Fuels, Clothes, Polymers, Drug, Agro-chemicals)
> 90 % of petro refining & petrochemicals processes use catalysts
90 % of processes & 60 % of products in the chemical industry
> 95% of pollution control technologies
Catalysis in the production/use of alternate fuels (NG,DME, H2, Fuel Cells, biofuels…)
1 Packing of spheres: Unit cell and description of crystal structure, close
packing of spheres, holes in closed-packed structures.
2 Structure of Metals: Polytypism, structures that are not closed packed, polymorphism of metals, atomic radii of metals, alloys.
3 Ionic solids: Characteristic structures of ionic solids, the rationalization of structures, the energetics of ionic bonding, consequences of lattice enthalpy.
In this presentation almost complete data are available like synthesis techniques,properties, functionalisations and Applications, etc. This is very useful for Students who studied about Silicides.
The study of crystal geometry helps to understand the behaviour of solids and their
mechanical,
electrical,
magnetic
optical and
Metallurgical properties
content-
Chemistry & Chemical Engineering
History of Catalysis
Catalysis
Recent trends in Catalysis
Future trends in Catalysis
Summary
role-
24% of GDP from Products made using catalysts (Food, Fuels, Clothes, Polymers, Drug, Agro-chemicals)
> 90 % of petro refining & petrochemicals processes use catalysts
90 % of processes & 60 % of products in the chemical industry
> 95% of pollution control technologies
Catalysis in the production/use of alternate fuels (NG,DME, H2, Fuel Cells, biofuels…)
1 Packing of spheres: Unit cell and description of crystal structure, close
packing of spheres, holes in closed-packed structures.
2 Structure of Metals: Polytypism, structures that are not closed packed, polymorphism of metals, atomic radii of metals, alloys.
3 Ionic solids: Characteristic structures of ionic solids, the rationalization of structures, the energetics of ionic bonding, consequences of lattice enthalpy.
In this presentation almost complete data are available like synthesis techniques,properties, functionalisations and Applications, etc. This is very useful for Students who studied about Silicides.
The study of crystal geometry helps to understand the behaviour of solids and their
mechanical,
electrical,
magnetic
optical and
Metallurgical properties
How do we describe the bonding between transition metal (ions) and their ligands (like water, ammonia, CO etc) ?
The Crystal Field Model gives a simple theory to explain electronic spectra.
1. Chapter 2 - 1
Properties depend on
- arrangement of atoms
- interactions between atoms
Study Bonding:
• What promotes bonding?
• What types of bonds are there?
• What properties are inferred from bonding?
CHAPTER 2:
BONDING AND PROPERTIES
2. Chapter 2 - 2
Atomic Structure (Freshman Chem.)
• atom – electrons – 9.11 x 10-31
kg
protons
neutrons
• nucleus of atom: “size of a point on a page” -! فراغ
• atomic number = No. of protons in nucleus of atom
= No. of electrons of neutral species
A [=] atomic mass unit = amu = 1/12 mass of 12
C
Atomic wt = wt of 6.023 x 1023
molecules or atoms
Unit 1 amu/atom = 1g/mol
C 12.011
H 1.008 etc.
} 1.67 x 10-27
kg
3. Chapter 2 - 3
Atomic Structure
• Valence electrons: in the outer-shell
• determine all of the following properties
1) Chemical: reactivity
2) Electrical: conductivity
3) Thermal: conductivity
4) Optical: transmittance
4. Chapter 2 - 4
Electronic Structure - Review
• Electrons have wavelike and particulate properties.
– This means that electrons are in orbitals defined by a
probability.
– Each orbital at discrete energy level determined by
quantum numbers.
Quantum # Designation
n = principal (energy level-shell) K, L, M, N, O (1, 2, 3, etc.)
l = subsidiary (orbitals) s, p, d, f (0, 1, 2, 3,…, n-1)
ml = magnetic (direction in space) 1, 3, 5, 7 (-l to +l)
ms = spin ½, -½
5. Chapter 2 - 5
Electron Energy States
1s
2s
2p
K-shell n = 1
L-shell n = 2
3s
3p M-shell n = 3
3d
4s
4p
4d
Energy
N-shell n = 4
• have discrete energy states
• tend to occupy lowest available energy state.
Electrons...
6. Chapter 2 - 6
• Why? Valence (outer) shell usually not filled completely.
• Most elements: Electron configuration not stable.
SURVEY OF ELEMENTS - Review
Electron configuration
(stable)
...
...
1s22s22p 63s23p 6 (stable)
...
1s22s22p 63s23p 63d 10 4s24p6 (stable)
Atomic #
18
...
36
Element
1s11Hydrogen
1s22Helium
1s22s13Lithium
1s22s24Beryllium
1s22s22p 15Boron
1s22s22p 26Carbon
...
1s22s22p 6 (stable)10Neon
1s22s22p 63s111Sodium
1s22s22p 63s212Magnesium
1s22s22p 63s23p 113Aluminum
...
Argon
...
Krypton
7. Chapter 2 - 7
Electron Configurations
• Valence electrons – those in unfilled shells
• Filled shells more stable
• Valence electrons are most available for bonding and
tend to control the chemical properties
• Primary Bonding: Ionic, Covalent and Metallic
• example: C (atomic number = 6)
1s2
2s2
2p2
valence electrons
8. Chapter 2 - 8
Electronic Configurations
ex: Fe - atomic # = 26
valence
electrons
1s
2s
2p
K-shell n = 1
L-shell n = 2
3s
3p M-shell n = 3
3d
4s
4p
4d
Energy
N-shell n = 4
1s2
2s2
2p6
3s2
3p6
3d6
4s2
9. Chapter 2 - 9
The Periodic Table
• Columns: Similar Valence Structure
Electropositive elements:
Readily give up electrons
to become + ions.
Electronegative elements:
Readily acquire electrons
to become - ions.
giveup1e
giveup2e
giveup3e
inertgases
accept1e
accept2e
O
Se
Te
Po At
I
Br
He
Ne
Ar
Kr
Xe
Rn
F
ClS
Li Be
H
Na Mg
BaCs
RaFr
CaK Sc
SrRb Y
10. Chapter 2 - 10
• Ranges from 0.7 to 4.0,
Smaller electronegativity Larger electronegativity
• Large values: tendency to acquire electrons.
Electronegativity
12. Chapter 2 - 12
• Occurs between + and - ions.
• Requires electron transfer.
• Large difference in electronegativity required.
• Example: NaCl
Ionic Bonding
Na (metal)
unstable
Cl (nonmetal)
unstable
electron
+ -
Coulombic
Attraction
Na (cation)
stable
Cl (anion)
stable
13. Chapter 2 - 13
• Predominant bonding in Ceramics
Examples: Ionic Bonding
Give up electrons Acquire electrons
NaCl
MgO
CaF2
CsCl
14. Chapter 2 - 14
C: has 4 valence e -
,
needs 4 more
H: has 1 valence e -
,
needs 1 more
Electronegativities
are comparable.
Covalent Bonding
• similar electronegativity ∴ share electrons
• bonds determined by valence – s & p orbitals
dominate bonding
• Example: CH4
shared electrons
from carbon atom
shared electrons
from hydrogen
atoms
H
H
H
H
C
CH4
15. Chapter 2 - 15
Primary Bonding
• Metallic Bond -- delocalized as electron cloud
• Ionic-Covalent Mixed Bonding
% ionic character =
where XA & XB are Pauling electronegativities
%)100(x1−e
−
(XA−XB)2
4
ionic70.2%(100%)xe1characterionic% 4
)3.15.3( 2
=
−=
−
−
Ex: MgO XMg = 1.3
XO = 3.5
21. Chapter 2 - 21
Bonding Curve
• Energy – minimum energy most stable
– Energy balance of attractive and repulsive terms
Attractive energy EA
Net energy EN
Repulsive energy ER
Interatomic separation r
r
A
n
r
B
EN = EA + ER = −−ro
22. Chapter 2 - 22
Bonding - Estimations
• Estimation of Bonding Energy (Eo) and Equilibrium Spacing (ro)
• Given:
• Bonding occurs at energy minimum
• At minimum: Derivative dE/dr = g(r) = 0
• Solve g(r) = 0 for r ro
• Substitute r=ro in the Energy Eqn:
• Get Eo = E (r=ro)
• Atomic radius R = ro/2
Eo =
“bond energy”
Energy
ro
r
r
A
n
r
B
E = certain f(r) e.g. E = −
For many atoms, ro is approximately 0.3 nm.
23. Chapter 2 - 23
• Bond length, r
• Bond energy, Eo
• Melting Temperature, Tm
Tm is larger if Eo is larger.
Properties From Bonding: Tm
ro
r
Energy
r
larger Tm
smaller Tm
Eo =
“bond energy”
Energy
ro
r
unstretched length
24. Chapter 2 - 24
• Coefficient of thermal expansion, α
• α ~ symmetry at ro
α is larger if Eo is smaller.
Properties From Bonding : α
= α (T2-T1)
∆L
Lo
Coefficient of thermal expansion
∆L
length, Lo
unheated, T1
heated, T2
ro
r
Smaller α
Larger α
Energy
unstretched length
Eo
Eo
25. Chapter 2 - 25
Ceramics
(Ionic & covalent bonding):
Metals
(Metallic bonding):
Polymers
(Covalent & Secondary):
Large bond energy
large Tm
large E
small α
Variable bond energy
moderate Tm
moderate E
moderate α
Directional Properties
Secondary bonding dominates
small Tm
small E
large α
Summary: Primary Bonds
secondary bonding
Bonding in Solids > Liquids > Gases
26. Chapter 2 - 26
Reading: Focus on Atomic Bonding in Solids
Core Problems:
2.7, 2.8, 2.12, 2.13,
2.17, 2.19, 2.21 (Callister 3rd
Addition)
Quiz: Next Class
ANNOUNCEMENTS
27. Chapter 2 - 27
Quiz
Energy
Atomic Spacing rA
B
c
Rank materials A, B and C according to
1. Increasing melting temperature > >
2. Decreasing bonding energy > >
3. Increasing Atomic Radius > >
4. Increasing coefficient of thermal expansion > >
28. Chapter 2 - 28
Quiz
Energy
Atomic Spacing r
A
B
c
Rank materials A, B and C according to
1. Increasing melting temperature > >
2. Decreasing bonding energy > >
3. Increasing Atomic Radius > >
4. Increasing coefficient of thermal expansion > >
![Chapter 2 - 2
Atomic Structure (Freshman Chem.)
• atom – electrons – 9.11 x 10-31
kg
protons
neutrons
• nucleus of atom: “size of a point on a page” -! فراغ
• atomic number = No. of protons in nucleus of atom
= No. of electrons of neutral species
A [=] atomic mass unit = amu = 1/12 mass of 12
C
Atomic wt = wt of 6.023 x 1023
molecules or atoms
Unit 1 amu/atom = 1g/mol
C 12.011
H 1.008 etc.
} 1.67 x 10-27
kg](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)