ATOMIC STRUCTURE AND INTERATOMIC BONDING INTERATOMIC BONDING INTRODUCTION O ATOMIC STRUCTURE Fundamental Concepts Electrons in Atoms OBJECTIVE Name the two atomic models cited, and Electrons in Atoms The Periodic Table ATOMIC BONDING IN SOLIDS note the differences between them. Describe the important quantum mechanical principle that relates to electron energies. Bonding Forces and Energies Primary Interatomic Bonds Secondary Bonding or van der Waals Bonding Schematically plot attractive, repulsive, and net energies versus interatomic separation for two atoms or ions. Note on this plot the equilibrium separation Bonding Molecules Summary Important Terms and Concepts and the bonding energy. Briefly describe ionic, covalent, metallic, hydrogen, and van der Waals bonds. Note which materials exhibit each of these Note which materials exhibit each of these bonding types.
62
Embed
ATOMIC STRUCTURE AND INTERATOMIC ... - …webstaff.kmutt.ac.th/~itasapun/PHY321/บทที่ 2... · ATOMIC STRUCTURE AND INTERATOMIC BONDINGINTERATOMIC BONDING INTRODUCTION O
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
ATOMIC STRUCTURE AND
INTERATOMIC BONDINGINTERATOMIC BONDING
INTRODUCTION
OATOMIC STRUCTURE Fundamental Concepts Electrons in Atoms
OBJECTIVE
Name the two atomic models cited, and Electrons in Atoms The Periodic Table
ATOMIC BONDING IN SOLIDS
,note the differences between them.
Describe the important quantum mechanical principle that relates to electron energies.
Bonding Forces and Energies Primary Interatomic Bonds Secondary Bonding or van der WaalsBonding
Schematically plot attractive, repulsive, and net energies versus interatomic separation for two atoms or ions.
Note on this plot the equilibrium separation Bonding Molecules Summary Important Terms and Concepts
p q pand the bonding energy.
Briefly describe ionic, covalent, metallic, hydrogen, and van der Waals bonds.
Note which materials exhibit each of these
Note which materials exhibit each of these bonding types.
(b) Wave mechanical atom models in terms of electron distributionterms of electron distribution.
(a) The first three electron energy states for the Bohr hydrogen atom.b) Electron energ states for the first three shells of the a e(b) Electron energy states for the first three shells of the wave-
mechanical hydrogen atom.
QUANTUM NUMBERQUANTUM NUMBER
Using wave mechanics, every electron in an atom is characterized by four parameters called quantum numbers. The size shape and spatial orientation of an electron’sThe size, shape, and spatial orientation of an electron sprobability density are specified by three of these quantum numbersnumbers
1. Principal quantum number, n2. Second quantum number, l3 Thi d t b3. Third quantum number, ml.
4. The fourth quantum number, s
Principle quantum number (n)
( h ll )
Principle quantum number (n)
ระดบขนพลงงานหลก ( shell ) ถกแสดงดวยเลขควอนตม
หลก( principle quantum number ) n เรมจาก 1, 2,3..... ( p c p e qua tu u be ) , ,3.....
แทนไดดวยอกษร K,L M, N ……..
จะบอกถงระยะหางของอเลคตรอน จากนวเคลยส
Orbital quantum number (l)
ป
Orbital quantum number (l)
l บงบอกถงระดบพลงงานยอย และรปรางของออบทล
l = 0 1 2 n 1 มความสมพนธกบโมเมนตม l = 0, 1, 2 , … , n-1 มความสมพนธกบโมเมนตม
2( ) Al i f il d f t i2(a) Aluminum foil used for storing food weighs about 0.3 g per square inch. g g p qHow many atoms of aluminum are contained in this sample of foil?contained in this sample of foil?
2 (b) Using the densities and atomic weights ( ) g ggiven in periodic table, calculate and compare the number of atoms per cubic centimeter inthe number of atoms per cubic centimeter in (a) lead and (b) lithium.
3 Indium which has an atomic number of 493. Indium, which has an atomic number of 49, contains no electrons in its 4f energy level. Based only on this information what must beBased only on this information, what must be the valence of indium?
The electronegativity values for the elements. (Adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition. Copyright 1939 and 1940, 3rd edition copyright 1960, by Cornell University. Used by permission of the publisher, Cornell University Press.)
ELECTRONEGATIVITY• Ranges from 0.7 to 4.0,• Large values: tendency to acquire electrons.
He -
N F Li
H 2.1
Be
Large values: tendency to acquire electrons.
Ne -
Ar -
Kr
F 4.0
Cl 3.0
Br
Li 1.0
Na 0.9
K
Be 1.5
Mg 1.2
Ca Ti Cr Fe Ni Zn As Kr -
Xe -
Rn
Br 2.8
I 2.5
At
K 0.8
Rb 0.8
Cs
Ca 1.0
Sr 1.0
Ba
Ti 1.5
Cr 1.6
Fe 1.8
Ni 1.8
Zn 1.8
As 2.0
Rn -
At 2.2
Cs 0.7
Fr 0.7
Ba 0.9
Ra 0.9
Smaller electronegativity Larger electronegativityAd t d f Fi 2 7 C lli t 6 (Fi 2 7 i d t d f Li P li Th N t f th
7
Adapted from Fig. 2.7, Callister 6e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by CornellUniversity.
ตารางธาต THE PERIODIC TABLE
• Columns: Similar Valence Structure
ase
s 1
e
e
ne
rt g
ae
pt
1e
ep
t 2
e
ve u
p u
p 2
e3
e
Metal
He
Ne
ina
cc
ea
cc
e
gi
giv
eve
up
3
F Li Be
Nonmetal
Intermediate
H
O Ne
Ar
Kr
giv
F Li Be
Na Cl
Br
O
S Mg
Ca K Sc Se
Adapted from Fig. 2.6, Callister 6e.
Xe
Rn
I
At
Sr
Ba
Ra
Rb
Cs
Fr
Y Te
Po
Electropositive elements:Readily give up electrons
The electronic structures, obtained from Appendix C, are:
Ca: 1s22s22p63s23p6 4s2
Br: 1s22s22p63s23p63d10 4s24p5
Calcium has two electrons in its outer 4s orbital and bromine has seven electrons in its outer 4s4p orbital. Calcium, with an electronegativity of 1.0, tends to give up electrons and has low electronegativity but bromine with an electronegativity of 2 8 electronegativity, but bromine, with an electronegativity of 2.8, tends to accept electrons and is strongly electronegative. This difference in electronegativity values suggests that these elements may react readily to form a compoundelements may react readily to form a compound.
IONIC BONDING• Occurs between + and - ions.• Requires electron transfer.q• Large difference in electronegativity required.• Example: NaCl
Na (metal) Cl (nonmetal)
p
( )unstable
( )unstable
electron
+ - Na (cation) t bl
Cl (anion) Coulombic Attraction
stable stable
8
EXAMPLES: IONIC BONDING• Predominant bonding in Ceramics
NaCl
He H
MgO
CaF2
NaCl
-
Ne -
Ar
F 4.0
Cl 3 0
Li 1.0
Na 0 9
2.1Be 1.5
Mg 1 2
CsClCaF2
O 3.5
-
Kr -
Xe -
3.0
Br 2.8
I 2 5
0.9
K 0.8
Rb 0 8
1.2
Ca 1.0
Sr 1 0
Ti 1.5
Cr 1.6
Fe 1.8
Ni 1.8
Zn 1.8
As 2.0
-
Rn -
2.5
At 2.2
0.8
Cs 0.7
Fr 0 7
1.0
Ba 0.9
Ra 0 9
Give up electrons Acquire electrons
0.7 0.9
Ad t d f Fi 2 7 C lli t 6 (Fi 2 7 i d t d f Li P li Th N t f th
9
Adapted from Fig. 2.7, Callister 6e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by CornellUniversity.
COVALENT BONDING• Requires shared electrons E l CH• Example: CH4
C: has 4 valence e,d 4
shared electrons from carbon atomH
CH4needs 4 more
H: has 1 valence e,d 1
HH C
needs 1 more
Electronegativitiesshared electrons from hydrogen
tH
are comparable. atoms
Adapted from Fig. 2.10, Callister 6e.
10
EXAMPLES: COVALENT BONDING
C(di d)
H2OH2 F2
mn
IVA
He -
Ne F Li
H 2.1
Be SiC
C(diamond)
C
Cl2
2
O
co
lum
-
Ar -
Kr
4.0
Cl 3.0
Br 2 8
1.0
Na 0.9
K 0 8
1.5
Mg 1.2
Ca 1 0
Ti 1 5
Cr 1 6
Fe 1 8
Ni 1 8
Zn 1 8
As 2 0
2.5
Si 1.8
Ga 1 6
Ge 1 8
2.0
-
Xe -
Rn
2.8
I 2.5
At 2 2
0.8
Rb 0.8
Cs 0 7
1.0
Sr 1.0
Ba 0 9
1.5 1.6 1.8 1.8 1.8 2.01.6 1.8
Sn 1.8Pb 1 8 -2.20.7
Fr 0.7
0.9
Ra 0.9 GaAs
1.8
Adapted from Fig. 2.7, Callister 6e. (Fig. 2.7 isadapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University.
• Molecules with nonmetals• Molecules with metals and nonmetals El t l lid (RHS f P i di T bl )
1.Bonding in the intermetallic compoundNi3Al is predominantly metallic. Explain whythere will be little, if any, ionic bonding, y, gcomponent. The electronegativity of nickel isabout 1 8about 1.8.
Problem
2 Aluminum has a density of 2 7 g/cm3 Suppose you2. Aluminum has a density of 2.7 g/cm3. Suppose youwould like to produce a composite material based onaluminum having a density of 1 5 g/cm3 Design aaluminum having a density of 1.5 g/cm3. Design amaterial that would have this density. Wouldintroducing beads of polyethylene with a density ofintroducing beads of polyethylene, with a density of0.95 g/cm3, into the aluminum be a likely possibility?ExplainExplain.
Problem
3.You would like to be able to physically separate differentt i l i li l t D ib iblmaterials in a scrap recycling plant. Describe some possible
methods that might be used to separate materials such aspolymers aluminum alloys and steels from one anotherpolymers, aluminum alloys, and steels from one another.
Problem
4.You would like to be able to identify different materialswithout resorting to chemical analysis or lengthy testingwithout resorting to chemical analysis or lengthy testingprocedures. Describe some possible testing and sortingtechniques you might be able to use based on the physicaltechniques you might be able to use based on the physicalproperties of materials.