ch02-materials science
TRANSCRIPT
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 1/28
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?
CHAPTE 2!
"#$%&$' A$% P#PET&E(
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 2/28
Chapter 2 - 2
Atomic (tr)ct)re *+reshman Chem,
• atom . e/ectrons . 0,11 1-31
4gprotons ne)trons
• n)c/e)s of atom! 5si6e of a point on a page7 -8 فر
• atomic n)mber 9 $o, of protons in n)c/e)s of atom 9 $o, of e/ectrons of ne)tra/ species
A :9; atomic mass )nit 9 am) 9 1<12 mass of 12C
Atomic wt 9 wt of =,23 123 mo/ec)/es or atoms
>nit 1 am)<atom 9 1g<mo/
C 12,11
H 1, etc,
} 1,=@ 1-2@ 4g
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 3/28
Chapter 2 - 3
Atomic (tr)ct)re
• a/ence e/ectrons! in the o)ter-she//
• determine a// of the fo//owing properties
1 Chemica/! reactiBity
2 E/ectrica/! cond)ctiBity
3 Therma/! cond)ctiBity
#ptica/! transmittance
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 4/28
Chapter 2 -
E/ectronic (tr)ct)re - eBiew
• Electrons have wavelike and particulate properties. . This means that e/ectrons are in orbita/s defined by a
probabi/ity,
. Each orbita/ at discrete energy /eBe/ determined by
D)ant)m n)mbers,
)ant)m F %esignation
n 9 principa/ *energy /eBe/-she// K G LG M G N G O *1G 2G 3G etc,
l 9 s)bsidiary *orbita/s sG pG d G f *G 1G 2G 3GG n -1
ml 9 magnetic *direction in space 1G 3G IG @ *-l to Jl
ms 9 spin KG -K
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 5/28
Chapter 2 - I
E/ectron Energy (tates
1s
2s2 p
K -she// n 9 1
L-she// n 9 2
3s3 p M -she// n 9 3
3d
s
pd
Energy
N -she// n 9
• haBe discrete energy states• tend to occ)py /owest aBai/ab/e energy state,
E/ectrons,,,
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 6/28
Chapter 2 - =
• Why? a/ence *o)ter she// )s)a//y not fi//ed comp/ete/y,
• Lost e/ements! E/ectron config)ration not stab/e,
(>EM #+ ENELE$T( - eBiew
E/ectron config)ration
*stab/e
,,,
,,,
1s22s22 p =3s23 p = *stab/e,,,
1s22s22 p =3s23 p =3d 1 s2 p= *stab/e
Atomic F
1,,,
3=
E/ement1s1 1Hydrogen
1s22He/i)m
1s22s1 3Nithi)m
1s22s2"ery//i)m
1s22s22 p 1I"oron
1s22s22 p 2=Carbon,,,
1s22s22 p = *stab/e1$eon1s22s22 p =3s111(odi)m
1s22s22 p =3s2 12Lagnesi)m
1s22s22 p =3s23 p 113 A/)min)m,,,
Argon,,,
Orypton
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 7/28
Chapter 2 - @
E/ectron Config)rations
• a/ence e/ectrons . those in )nfi//ed she//s• +i//ed she//s more stab/e• a/ence e/ectrons are most aBai/ab/e for bonding and
tend to contro/ the chemica/ properties
• Primary Bonding! &onicG CoBa/ent and Leta//ic
• eamp/e! C *atomic n)mber 9 =
1s2 2s2 2 p2
Ba/ence e/ectrons
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 8/28
Chapter 2 -
E/ectronic Config)rationse! +e - atomic F 9 2=
Ba/ence
e/ectrons
1s
2s2 p
K -she// n 9 1
L-she// n 9 2
3s3 p M -she// n 9 3
3d
s
pd
Energy
N -she// n 9
1s2 2s2 2 p= 3s2 3 p= 3d = s2
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 9/28
Chapter 2 - 0
The Periodic Tab/e• Co/)mns! (imi/ar a/ence (tr)ct)re
E/ectropositiBe e/ements!
eadi/y giBe )p e/ectrons
to become J ions,
E/ectronegatiBe e/ements!
eadi/y acD)ire e/ectrons
to become - ions,
g i B e
) p 1
e
g i B e
) p
2 e
g i B e
) p
3 e
i n e r t g a s
e s
a c c e p t 1 e
a c c e p t 2 e
#
(e
Te
Po At
&
"r
He
$e
Ar
Or
e
n
+
C/(
Ni "e
H
$a Lg
"aCs
a+r
CaO (c
(r b M
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 10/28
Chapter 2 - 1
• anges from ,@ to ,G
(ma//er e/ectronegatiBity Narger e/ectronegatiBity
• Narge Ba/)es! tendency to acD)ire e/ectrons,
E/ectronegatiBity
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 11/28
Chapter 2 - 11
&onic bond . meta/ J nonmeta/
donates accepts
e/ectrons e/ectrons%issimi/ar e/ectronegatiBities
e! Lg# Lg 1s2 2s2 2 p= 3s2 # 1s2 2s2 2 pC
:$e; 3s2
Lg2J 1s2 2s2 2 p= #2- 1s2 2s2 2 p=
:$e; :$e;
1s22s22 p = *stab/e1$eon
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 12/28
Chapter 2 - 12
• #cc)rs between J and - ions,
• eD)ires e/ectron transfer,• Narge difference in e/ectronegatiBity reD)ired,
• Eamp/e! $aC/
&onic "onding
$a *meta/)nstab/e
C/ *nonmeta/)nstab/e
e/ectron
+ -Co)/ombic
Attraction
$a *cationstab/e
C/ *anionstab/e
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 13/28
Chapter 2 - 13
• Predominant bonding in Ceramics
Eamp/es! &onic "onding
'iBe )p e/ectrons AcD)ire e/ectrons
$aC/
Lg#
Ca+2CsC/
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 14/28
Chapter 2 - 1
C! has Ba/ence e-
G needs more
H! has 1 Ba/ence e -G
needs 1 more
E/ectronegatiBities are comparab/e,
CoBa/ent "onding• simi/ar e/ectronegatiBity ∴ share e/ectrons
• bonds determined by Ba/ence . s Q p orbita/sdominate bonding
• Eamp/e! CHshared e/ectronsfrom carbon atom
shared e/ectrons
from hydrogenatoms
H
H
H
H
C
CH
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 15/28
Chapter 2 - 1I
Primary "onding
• Leta//ic "ond -- de/oca/i6ed as e/ectron c/o)d
• &onic-CoBa/ent Lied "onding
R ionic character 9
where X A Q X " are Pa)/ing e/ectronegatiBities
R1*1−e−
* X A− X " 2
C
ionic@,2R*1R-e1character ionicR
3,1I,3*
2
=
−=
−−
E! Lg# X Lg 9 1,3
X # 9 3,I
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 16/28
Chapter 2 - 1=
Arises from interaction between dipo/es
• Permanent dipo/es-mo/ec)/e ind)ced
• +/)ct)ating dipo/es
-genera/ case!
-e! /iD)id HC/
-e! po/ymer
Adapted from +ig, 2,1G
Callister 7e.
(EC#$%AM "#$%&$'
asymmetric e/ectron
c/o)ds
J - J -
secondarybonding
HH HH
H2 H2
secondarybonding
e! /iD)id H2
H C/ H C/secondary
bonding
secondarybonding
J - J -
secondary bondings e c o n d ar y b o n d i n g
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 17/28
Chapter 2 - 1@
Type
&onic
CoBa/ent
Leta//ic
(econdary
"ond Energy
Narge8
ariab/e
/arge-%iamondsma//-"ism)th
ariab/e/arge-T)ngstensma//-Lerc)ry
sma//est
Comments
$ondirectiona/ *ceramics
%irectiona/
*semicond)ctorsG ceramicspo/ymer chains
$ondirectiona/ *meta/s
%irectiona/
inter-chain *po/ymer
inter-mo/ec)/ar
()mmary! "onding
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 18/28
Chapter 2 - 1
&nteractions "etween Atoms
J-
J-
r
J-
J-
(pacing *r
Atomic adi)s *
+ar Atoms! Attraction C/ose Atoms! Repulsion
ED)i/ibri)m spacing 9 r o
r o 9 2
J
-
J
-
Dynamic Equilirium
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 19/28
Chapter 2 - 10
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 20/28
Chapter 2 - 2
"onding C)rBe
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 21/28
Chapter 2 - 21
"onding C)rBe
• Energy . minim)m energy most stab/e . Energy ba/ance of attractiBe and rep)/siBe terms
AttractiBe energy E A
$et energy E N
ep)/siBe energy E R
&nteratomic separation r
r A
nr B
E N 9 E A + E R 9 −−r o
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 22/28
Chapter 2 - 22
"onding - Estimations
• Estimation of "onding Energy *E o and ED)i/ibri)m (pacing *r o• 'iBen!
• "onding occ)rs at energy minim)m
• At minim)m! %eriBatiBe dE<dr 9 g*r 9
• (o/Be g*r 9 for r r o
• ()bstit)te r9r o in the Energy EDn!
• 'et Eo 9 E *r9r o
• Atomic radi)s 9 r o<2E o 9
5bond energy7
Energy
r o r
r A
nr B
E 9 certain f(r) e.g. E 9 −
!or many atoms" r o is appro#imately $.% nm.
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 23/28
Chapter 2 - 23
• "ond /engthG r
• "ond energyG E o
• Le/ting Temperat)reG m
m is /arger if E o is /arger,
Properties +rom "onding! m
r o r
Energy
r
/arger m
sma//er m
E o 9
5bond energy7
Energy
r o
r
)nstretched /ength
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 24/28
Chapter 2 - 2
• Coefficient of therma/ epansionG α
• α S symmetry at r o
α is /arger if E o is sma//er,
Properties +rom "onding ! α
=α * 2 - 1∆L
Lo
Coefficient of therma/ epansion
∆L
/engthG Lo
)nheatedG 1
heatedG 2
r or
(ma//er α
Narger α
Energy
)nstretched /ength
E !
E !
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 25/28
Chapter 2 - 2I
Ceramics
*&onic Q coBa/ent bonding!
Leta/s
*Leta//ic bonding!
Po/ymers
*CoBa/ent Q (econdary!
Narge bond energy
/arge m/arge E
sma// α
ariab/e bond energymoderate mmoderate E
moderate α
%irectiona/ Properties
(econdary bonding dominates sma// m sma// E
/arge α
()mmary! Primary "onds
s e c o n d ar y b o n d i n g
Bonding in Solids & 'iquids & (ases
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 26/28
Chapter 2 - 2=
Reading! +oc)s on Atomic "onding in (o/ids
)ore Prolems!
2,@G 2,G 2,12G 2,13G
2,1@G 2,10G 2,21 *Ca//ister 3rd Addition
*ui+! $et C/ass
A$$#>$CELE$T(
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 27/28
Chapter 2 - 2@
)i6
Energy
Atomic Spacing r
A"
c
Rank materials A" B and ) according to1, &ncreasing me/ting temperat)re
2, %ecreasing bonding energy
3, &ncreasing Atomic adi)s
, &ncreasing coefficient of therma/ epansion
7/24/2019 ch02-materials science
http://slidepdf.com/reader/full/ch02-materials-science 28/28
Chapter 2 - 2
)i6
Energy
Atomic Spacing r
A
B
c
Rank materials A" B and ) according to1, &ncreasing me/ting temperat)re
2, %ecreasing bonding energy
3, &ncreasing Atomic adi)s
, &ncreasing coefficient of therma/ epansion