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Chapter 3
Structure and Properties of
Ionic and CovalentCompounds
Denniston
Topping
Caret
5th Edition
Copyright The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
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3.1 Chemical Bonding
• Chemical bond - the force of attraction
between any two atoms in a compound
• This attractive force overcomes the
repulsion of the positively charged nuclei of
the two atoms participating in the bond
• Interactions involving valence electrons are
responsible for the chemical bond
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3 . 1 C
h e m i c a
l B o n d i n g ewis !ymbols
• ewis symbol "ewis structure# - a way torepresent atoms using the element symboland valence electrons as dots
• $s only valence electrons participate in bonding% this ma&es it much easier to wor&with the octet rule
• The number of dots used correspondsdirectly to the number of valence electronslocated in the outermost shell of the atoms
of the element
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3 . 1 C
h e m i c a
l B o n d i n g ewis !ymbols
• 'ach (side) of the symbol represents an atomicorbital% which may hold up to two electrons
• *sing ewis symbols
+ ,lace one dot on each side until there are four dots around
the symbol
+ ow add a second dot to each side in turn
+ The number of valence electrons limits the number ofdots placed
+ 'ach unpaired dot "unpaired electron of the valence shell#is available to form a chemical bond
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ewis ot !ymbols for
/epresentative 'lements
3 . 1 C
h e m i c a
l B o n d i n g
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3 . 1 C
h e m i c a
l B o n d i n g
,rincipal Types of Chemical Bonds0
Ionic and Covalent
• Ionic bond - a transfer of one or moreelectrons from one atom to another
• orms attractions due to the opposite charges of
the atoms
• Covalent bond - attractive force due to thesharing of electrons between atoms
• !ome bonds have characteristics of bothtypes and not easily identified as one or theother
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Ionic Bonding
• /epresentative elements form ions thatobey the octet rule
• Ions of opposite charge attract each other
creating the ionic bond• 2hen electrons are lost by a metal and
electrons are gained by a nonmetal
+ 'ach atom achieves a (oble as)configuration
+ 4 ions are formed5 a cation and anion% whichare attracted to each other
3 . 1 C
h e m i c a
l B o n d i n g
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3 . 1 C
h e m i c a
l B o n d i n g
Consider the formation of
aCl
a 6 Cl aCl
!odium has a low
ioni7ation energy it
readily loses this
electron a a6 6 e-
2hen sodium loses the
electron% it gains the
e configuration
Chlorine has a high
electron affinity
2hen chlorine gainsan electron% it gains
the $r configuration
−
−
!"#$%&'+( 0..
..Cl0e
..
..Cl0
Ionic Bonding
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3 . 1 C h
e m i c a l
B o n d i n g
'ssential eatures of Ionic Bonding
• $toms with low I.'. and low '.$. tend to form positive ions
• $toms with high I.'. and high '.$. tend to form
negative ions
• Ion formation ta&es place by electron transfer
• The ions are held together by the electrostatic
force of the opposite charges
• /eactions between metals and nonmetals
"representative elements# tend to be ionic
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Ion $rrangement in a Crystal
• $s a sodium atom loses one electron% it becomes asmaller sodium ion
• 2hen a chlorine atom gains that electron% it becomes a larger chloride ion
• $ttraction of the a cation with the Cl anionforms aCl ion pairs that aggregate into a crystal
3 . 1 C h
e m i c a l
B o n d i n g
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3 . 1 C
h e m i c a
l B o n d i n g Covalent Bonding
et8s loo& at the formation of 940
9 6 9 94• 'ach hydrogen has one electron in its valance shell• If it were an ionic bond it would loo& li&e this0
• 9owever% both hydrogen atoms have an e:ualtendency to gain or lose electrons
• 'lectron transfer from one 9 to another usually willnot occur under normal conditions
[ ]−+ +→⋅+⋅ 09999
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3 . 1 C
h e m i c a
l B o n d i n g
The shared
electron
pair is called a
Covalent Bond
'ach hydrogen
atom now has twoelectrons around it
and attained a 9e
configuration
• Instead% each atom attains a noble gas
configuration by sharing electrons
909 9 9 →⋅+⋅
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Covalent Bonding in 9ydrogen
3 . 1 C
h e m i c a
l B o n d i n g
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3 . 1 C
h e m i c a
l B o n d i n g
0
..
..10
..
..100
..
..1
..
..10 →⋅+⋅
'ach fluorine is
surrounded by ;
electrons + e
configuration
eatures of Covalent Bonds
• Covalent bonds form between atoms withsimilar tendencies to gain or lose electrons
• Compounds containing covalent bonds are
called covalent compounds or molecules• The diatomic elements have completely
covalent bonds "totally e:ual sharing#
+ 94% 4%
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90
..
..
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3 . 1 C
h e m i c a
l B o n d i n g
,olar Covalent Bonding and
'lectronegativity
• The ,olar Covalent Bond
+ Ionic bonding involves the transfer of
electrons + Covalent bonding involves the sharing of
electrons
+ Polar covalent bonding - bonds made upof unequally shared electron pairs
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3 . 1 C
h e m i c a
l B o n d i n g
These two
electrons are
not shared e:ually
somewhat negatively chargedsomewhat positively charged
0..090
..9
⋅⋅
→
⋅⋅
⋅+⋅
• The electrons spend more time with fluorine
• This sets up a polar covalent bond• $ truly covalent bond can only occur when
both atoms are identical
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,olar Covalent Bonding in 2ater
• ygen is electron rich @ δ-
• 9ydrogen is electron
deficient @ δ6
• This results in une:ual
sharing of electrons in the
pairs @ polar covalent bonds
• 2ater has 4 covalent bonds
3 . 1 C
h e m i c a
l B o n d i n g
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'lectronegativity
• Electronegativity - a measure of theability of an atom to attract electrons in a
chemical bond
• 'lements with high electronegativity havea greater ability to attract electrons than do
elements with low electronegativity
• Consider the covalent bond as competition
for electrons between 4 positive centers + The difference in electronegativity determines
the e>tent of bond polarity 3 . 1 C
h e m i c a
l B o n d i n g
'l t ti iti f ! l t d
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3 . 1 C
h e m i c a
l B o n d i n g
electronegativity increases e l e c t r o n e g a t i v i t y i n c r e a s e s
'lectronegativities of !elected
'lements
• The most electronegative elements are found in the upper rightcorner of the periodic table
• The least electronegative elements are found in the lower leftcorner of the periodic table
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3 . 1 C
h e m i c a
l B o n d
i n g 'lectronegativity Calculations
• The greater the difference in electronegativity between two atoms% the greater the polarity of
their bond
• 2hich would be more polar% a 9- bond or 9-Cl
bondA
• 9- =. - 4.1 @ 1.D
• 9-Cl 3. - 4.1 @ .D• The 9 bond is more polar than the 9Cl bond
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3.4 aming Compounds and
2riting ormulas of Compounds
• Nomenclature - the assignment of a correct
and unambiguous name to each and everychemical compound
• Two naming systems0
+ ionic compounds
+ covalent compounds
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i n g C o m p o u n d
s a n d
2
r i t i n g o r m u l a s o f C o m p o u n d s ormulas of Compounds
• $ formula is the representation of thefundamental compound using chemical
symbols and numerical subscripts
+ The formula identifies the number and typeof the various atoms that ma&e up the
compound unit
+ The number of li&e atoms in the unit is
shown by the use of a subscript + ,resence of only one atom is understood
when no subscript is present
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2
r i t i n g o r m u l a s o f C o m p o u n d s Ionic Compounds
• Eetals and nonmetals usually react to formionic compounds
• The metals are cations and the nonmetals
are anions• The cations and anions arrange themselves
in a regular three-dimensional repeatingarray called a crystal lattice
• ormula of an ionic compound is thesmallest whole-number ratio of ions in thesubstance
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2
r i t i n g o r m u l a s o f C o m p o u n d s 2riting ormulas of Ionic Compounds
from the Identities of the Component Ions
• etermine the charge of each ion
+ Eetals have a charge e:ual to group number
+ onmetals have a charge e:ual to the group
number minus eight
• Cations and anions must combine to give a
formula with a net charge of 7ero
• It must have the same number of positive
charges as negative charges
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i n g C o m p o u n d s a n d
2
r i t i n g o r m u l a s o f C o m p o u n d s ,redict ormulas
,redict the formula of the ionic compoundsformed from combining ions of the
following pairs of elements0
1. sodium and o>ygen
4. lithium and bromine
3. aluminum and o>ygen
=. barium and fluorine
2 i i f I i C d
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4
3 . 4 - a m
i n g C o m p o u n d s a n d
2
r i t i n g o r m u l a s o f C o m p o u n d s 2riting ames of Ionic Compounds
from the ormula of the Compound
• ame the cation followed by the nameof the anion
• $ positive ion retains the name of the
element5 change the anion suffi> to-ide
2 iti f I i C d
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r i t i n g o r m u l a s o f C o m p o u n d s 2riting ames of Ionic Compounds
from the ormula of the Compound
• If the cation of an element has several ions ofdifferent charges "as with transition metals# use a/oman numeral following the metal name
• /oman numerals give the charge of the metal
• '>amples0
• eCl3 is iron"III# chloride
• eCl4 is iron"II# chloride
• Cu< is copper "II# o>ide
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!toc& and Common ames for
Iron and Copper Ions
3 . 4 - a m
i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p o u n d s
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i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p o u n d s
Common Eonatomic Cations
and $nions
• Monatomic ions - ions consisting of a
single charged atom
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i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p o u n d s ,olyatomic Ions
• Polyatomic ions - ions composed of 4 ormore atoms bonded together with anoverall positive or negative charge
+ 2ithin the ion itself% the atoms are bondedusing covalent bonds
+ The positive and negative ions will be bonded to each other with ionic bonds
• '>amples0
• 9=6 ammonium ion
• !
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i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p o u n d sCommon ,olyatomic Cations and
$nions
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i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p o u n d s
ame These Compounds
1. 9=Cl
4. Ba!
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i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p o u n d s2riting ormulas of Ionic Compounds
rom the ame of the Compound
• etermine the charge of each ion
• 2rite the formula so that the resulting
compound is neutral
• '>ample0
Barium chloride0
Barium is 64% Chloride is -1ormula is BaCl4
t i th l
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i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p o u n d s etermine the ormulas rom
ames
2rite the formula for the following ionic
compounds0
1. sodium sulfate
4. ammonium sulfide
3. magnesium phosphate
=. chromium"II# sulfate
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i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p o u n d s Covalent Compounds
• Covalent compounds are typically formedfrom nonmetals
• Molecules - compounds characteri7ed by
covalent bonding• ot a part of a massive three-dimensional
crystal structure
• '>ist as discrete molecules in the solid% li:uid%and gas states
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i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p
o u n d s
aming Covalent Compounds
1. The names of the elements are writtenin the order in which they appear inthe formula
4. $ prefi> indicates the number of each&ind of atom
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3. If only one atom of a particular element is
present in the molecule% the prefi> mono- isusually omitted from the first element
'>ample0 C< is carbon mono>ide
=. The stem of the name of the last element isused with the suffi> +ide
F. The final vowel in a prefi> is often dropped before a vowel in the stem name
3 . 4 - a m
i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s o f C o m p
o u n d s aming Covalent Compounds
Th C l C d
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. 4 - a m
i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s
o f C o m p
o u n d s ame These Covalent Compounds
1. !i
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4
3
. 4 - a m
i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s
o f C o m p
o u n d s 2riting ormulas of Covalent
Compounds• *se the prefi>es in the names to determine the
subscripts for the elements
• '>amples0• nitrogen trichloride Cl3• diphosphorus pento>ide ,4
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. 4 - a m
i n g C o m p o u n d s a n d
2
r i t i n g
o r m u l a s
o f C o m p
o u n d s ,rovide ormulas for These
Covalent Compounds
1. nitrogen mono>ide
4. dinitrogen tetro>ide
3. diphosphorus pento>ide
=. nitrogen trifluoride
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3.3 ,roperties of Ionic and
Covalent Compounds• ,hysical !tate
+ Ionic compounds are usually solids at room
temperature + Covalent compounds can be solids% li:uids% and
gases
• Eelting and Boiling ,oints + Melting point - the temperature at which a
solid is converted to a li:uid
+ Boiling point - the temperature at which ali:uid is converted to a gas
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,hysical ,roperties
•Eelting and Boiling ,oints + Ionic compounds have much higher melting points
and boiling points than covalent compounds
+ $ large amount of energy is re:uired to brea& the
electrostatic attractions between ions + Ionic compounds typically melt at several hundred
degrees Celsius
• !tructure of Compounds in the !olid !tate
+ Ionic compounds are crystalline + Covalent compounds are crystalline or amorphous +
having no regular structure
3 . 3 , r o p e r t i e s o f I o n i c a n d
C o v a
l e n t C o
m p o u n
d s
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• !olutions of Ionic and Covalent
Compounds
+ Ionic compounds often dissolve in water%
where they dissociate - form positive and
negative ions in solution + Electrolytes - ions present in solution
allowing the solution to conduct electricity
+ Covalent solids usually do not dissociate anddo not conduct electricity - nonelectrolytes
,hysical ,roperties
3 . 3 , r o p e r t i e s o f I o n i c a n d
C o v a
l e n t C o
m p o u n
d s
C i f I i C l t
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Comparison of Ionic vs. Covalent
Compounds
Ionic Covalent
Composed of Eetal 6 nonmetal 4 nonmetals
'lectrons Transferred !hared
,hysical state !olid H crystal $ny H crystal
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3.= rawing ewis !tructures on
Eolecules and ,olyatomic Ions
Leis !tructure "uidelines
1. *se chemical symbols for the various
elements to write the s&eletal structure of
the compound
+ The least electronegative atom will be placed in
the central position
+ 9ydrogen and halogens occupy terminal positions
+ Carbon often forms chains of carbon-carbon
covalent bonds
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ewis !tructure uidelines
4. etermine the number of valenceelectrons associated with each atom in
the compound
+ Combine these valence electrons todetermine the total number of valence
electrons in the compound
+ ,olyatomic cations% subtract one electron for
every positive charge + ,olyatomic anions% add one electron for
every negative charge 3 . = r a w i n g e w i s
! t r u c t u r e s o f E o l e c u
l e s
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ewis !tructure uidelines
3. Connect the central atom to each of thesurrounding atoms using electron pairs
• e>t% complete octets of all the atoms
bonded to the central atom
• 9ydrogen needs only two electrons
• 'lectrons not involved in bonding are
represented as lone pairs
• Total number of electrons in the structure
must e:ual the number of valence electrons
in step 4 3 . = r a w i n g e w i s
! t r u c t u r e s o f E o l e c u
l e s
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=. Count the number of electrons you have
and compare to the number you used• If they are the same% you are finished
• If you used more electrons than you have%
add a bond for every two too many you used• Then% give every atom an octet
• If you used less electrons than you have.seelater e>ceptions to the octet rule
F. /echec& that all atoms have the octet rule
satisfied and that the total number of
valance electrons are used
3 . = r a w i n g e w i s
! t r u c t u r e s o f E o l e c u
l e s ewis !tructure uidelines
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rawing ewis !tructures of
Covalent Compoundsraw the ewis structure of carbon dio>ide% C
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F. ind the number of valence electrons for eachatom and the total for the compound
1 C atom > = valence electrons @ = e- 4 < atoms > ? valence electrons @ 14 e-
1? e- total
?. *se electron pairs to connect the C to each < witha single bond
< 0 C 0 <
G. ,lace electron pairs around the atoms
# < 0 C 0 < #
This satisfies the rule for the < atoms% but not for C
rawing ewis !tructures
3 . = r a w i n g e w i s
! t r u c t u r e s o f E o l e c u
l e s
# #
# #
rawing ewis !tructures of
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;. /edistribute the electrons moving 4 e- from each
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3 . = r a w i n g e w i s
! t r u c t u r e s o f E o l e c u
l e s
ewis !tructures ,ractice
*sing the guidelines presented% write ewis structuresfor the following0
1. 94<
4. 93
3. C
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?
3 . = r a w i n g e w i s
! t r u c t u r e s o f E o l e c u
l e s
ewis !tructures of
,olyatomic Ions
• ,repare ewis structures of polyatomic
ions as for neutral compounds% e>cept0
• The charge on the ion must be
accounted for when computing the
total number of valence electrons
ewis !tructure of
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ewis !tructure of
,olyatomic Cations
3 . = r a w i n
g e w i s
! t r u c t u r e s o f E o l e c u
l e s
raw the ewis structure of ammonium ion% 9=6
raw a s&eletal structure of the molecule
1. $mmonium has this structure and charge0
4. The total number of valence electrons is determined by
subtracting one electron for each unit of positivecharge
1 atom > F valence electrons @ F e-
= 9 atoms > 1 valence electron @ = e-
- 1 electron for 61 charge @ -1 e-
; e- total + istribute these ; e- around the s&eletal structure
ewis !tructure of ,olyatomic
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raw the ewis structure of carbonate ion% Cygen
• This ma&es carbon the central atom
• !&eletal structure and charge04. The total number of valence electrons is determined by
adding one electron for each unit of negative charge
1 C atom > = valence electrons @ = e-
3 < atoms > ? valence electron @ 1; e- 6 4 negative charges @ 4 e-
4= e- total + istribute these e- around the s&eletal structure
ewis !tructure of ,olyatomic
$nions
3 . = r a w i n
g e w i s
! t r u c t u r e s o f E o l e c u
l e s
ewis !tructure of ,olyatomic
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raw the ewis structure of carbonate ion% C
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• !ingle bond - one pair of electrons are
shared between two atoms
• Double bond - two pairs of electrons areshared between two atoms
• Triple bond - three pairs of electrons are
shared between two atoms
• Kery stable
ewis !tructure% !tability% Eultiple
Bonds% and Bond 'nergies
3 . = r a w i n
g e w i s
! t r u c t u r e s o f E o l e c u
l e s
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or.. ..
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3 . = r a w i n
g e w i s
! t r u c t u r e s o f E o l e c u
l e s ewis !tructures and /esonance
• 2rite the ewis structure of C
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• '>perimental evidence shows all bonds are
the same length% meaning there is not really
any double bond in this ion
• one of theses three ewis structures e>ist%
but the actual structure is an average or
hybrid of these three ewis structures
• &esonance - two or more ewis structures
that contribute to the real structure
0
..
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3 . = r a w i n
g e w i s
! t r u c t u r e s o f E o l e c u
l e s
ewis !tructures and '>ceptions
to the 4 valence electrons @ 4 e-
4 9 atoms > 1 valence electrons @ 4 e-
total = e-
+ /esulting ewis structure09 # Be # 9 or 9 ' Be ' 9
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3 . = r a w i n
g e w i s
! t r u c t u r e s o f E o l e c u
l e s
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3. '>panded octet - an element in the 3rd period or belowmay have 1 and 14 electrons around it
• '>panded octet is the most common e>ception
• Consider the ewis structure of ,F
• ,hosphorus is a third period element
1 , atom > F valence electrons @ F e-
F atoms > G valence electrons @ 3F e-
= e- total
3. istributing the electrons results in this ewis structure
3 . = r a w i n
g e w i s
! t r u c t u r e s o f E o l e c u
l e s '>panded
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3 . = r a w i n
g e w i s
! t r u c t u r e s o f E o l e c u
l e sewis !tructures and Eolecular
eometry0 K!',/ Theory
• Eolecular shape plays a large part indetermining properties and shape
• K!',/ theory - (alance !hell Electron Pair& epulsion theory
• *sed to predict the shape of the molecules
• $ll electrons around the central atom arrangethemselves so they can be as far away fromeach other as possible + to minimi7e electronicrepulsion
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3 . = r a w i n
g e w i s
! t r u c t u r e s o f E o l e c u
l e s K!',/ Theory
• In the covalent bond% bonding electronsare locali7ed around the nucleus
• The covalent bond is directional , having
a specific orientation in space betweenthe bonded atoms
• Ionic bonds have electrostatic forces
which have no specific orientation in
space
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Eolecular Bonding
• Bonding pair @ two electrons shared
by 4 atoms
+ 90<
• onbonding pair @ two electrons
belonging to 1 atom% pair not shared
+ 0
• Ea>imal separation of bonding pairs
@ = corners of a T'T/$9'/
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3 . = E o
l e c u l a r
e o m e t r y
$ !table '>ception to the
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3 . = E o
l e c u l a r
e o m e t r y
$nother !table '>ception to the
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3 . = E o
l e c u l a r
e o m e t r y
Basic 'lectron ,air /epulsion of
a ull
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3 . = E o
l e c u l a r
e o m e t r y
Basic 'lectron ,air /epulsion of
a ull
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3 . = E o
l e c u l a r
e o m e t r y
Basic 'lectron ,air /epulsion of
a ull
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,redicting eometric !hape *sing
'lectron ,airs
3 . = r a w i n
g e w i
s
! t r u c t u r e s o f
E o l e c u
l e s
Basic ,rocedure to etermine
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3 . = r a w i n
g e w i
s
! t r u c t u r e s o f
E o l e c u
l e s Eolecular !hape
1. 2rite the ewis structure
4. Count the number of shared electron pairs andlone pairs around the central atom
3. If no lone pairs are present% shape is0• 4 shared pairs - linear • 3 shared pairs - trigonal planar
• = shared pairs - tetrahedral
=. oo& at the arrangement and name the shape• inear • Trigonal planar • Bent• Trigonal pyramid• Tetrahedral
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3 . = E o
l e c u l a r e o m e t r y Eore Comple> Eolecules
Consider dimethyl ether • 9as 4 different central atoms0
• o>ygen
• carbon
+ C93 "methyl group# has tetrahedral geometry "li&e methane#
+ Portion o) the molecule lin*ing the to methyl groups ould bond angles similar to ater
etermine the Eolecular
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3 . = r a w i n
g e w i
s
! t r u c t u r e s o f
E o l e c u
l e s etermine the Eolecular
eometry
• ,Cl3
• !
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3 . = r a w i n
g e w i
s
! t r u c t u r e s o f
E o l e c u
l e s ewis !tructures and ,olarity
•$ molecule is polar if its centers of positive andnegative charges do not coincide
• ,olar molecules when placed in an electric fieldwill align themselves in the field
• Eolecules that are polar behave as a dipole "havingtwo (poles) or ends#
•
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,ositive end of the
bond% the less
electronegative atom
egative end of the bond%
more electronegative atom
attracts the electrons more
strongly towards it 3 . = r a w i n
g e w i
s
! t r u c t u r e s o f
E o l e c u
l e s etermining ,olarity
To determine if a molecule is polar0• 2rite the ewis structure
• raw the geometry
• *se the following symbol to denote the polarityof each bond
,ractice etermining ,olarity
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3 . = r a w i n
g e w i
s
! t r u c t u r e s o f
E o l e c u
l e s ,ractice etermining ,olarity
etermine whether the following bonds and
molecules are polar0
1. !i + Cl 1.
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3.F ,roperties Based on 'lectronic
!tructure and Eolecular eometry
• Intramolecular forces + attractive forces
within molecules + Chemical bonds
• Intermolecular forces + attractive forces
between molecules
• Intermolecular forces determine many
physical properties
+ Intermolecular forces are a direct conse:uence
of the intramolecular forces in the molecules
n i c t r y !olubility and Intermolecular
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!olubility - the ma>imum amount of solutethat dissolves in a given amount of solventat a specific temperature
• (i&e dissolves li&e) + ,olar molecules are most soluble in polar
solvents
+ onpolar molecules are most soluble in
nonpolar solvents• oes ammonia% 93% dissolve in waterA
• es% both molecules are polar
3
. F , r o p e
r t i e s B a s
e d o n ' l e c t r o n
!
t r u c t u r e
a n d E o l e c u l a r e o m e t
!olubility and Intermolecular
orces
n i c t r y Interaction of 2ater and
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3
. F , r o p e
r t i e s B a s
e d o n ' l e c t r o n
!
t r u c t u r e
a n d E o l e c u l a r e o m e t
$mmonia
• The δ- end of ammonia% % is attracted to the δ6 end ofthe water molecule% 9
• The δ6 end of ammonia% 9% is attracted to the δ- end ofthe water molecule% <
• The attractive forces% called hydrogen bonds% pullammonia into water% distributing the ammonia moleculesthroughout the water% forming a homogeneous solution
n i c t r y Interaction of 2ater and
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3
. F , r o p e
r t i e s B a s
e d o n ' l e c t r o n
!
t r u c t u r e
a n d E o l e c u l a r e o m e t Interaction of 2ater and )
• 2hyA
+ Because water is polar and
oil is nonpolar
• 2ater molecules e>ert their
attractive forces on other water
molecules
•
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3
. F , r o p e
r t i e s B a s
e d o n ' l e c t r o n
!
t r u c t u r e
a n d E o l e c u l a r e o m e t
g :
and Eelting ,oints of !olids
• 'nergy is used to overcome the
intermolecular attractive forces in a
substance% driving the molecules into a less
associated phase
• The greater the intermolecular force% the
more energy is re:uired leading to
+ 9igher melting point of a solid
+ 9igher boiling point of a li:uid
n i c t r y actors Influencing Boiling and
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3
. F , r o p e
r t i e s B a s
e d o n ' l e c t r o n
!
t r u c t u r e
a n d E o l e c u l a r e o m e t
g g
Eelting ,oints
• !trength of the attractive force holding the
substance in its current physical state
• Eolecular mass
• arger molecules have higher m.p. and b.p. than
smaller molecules as it is more difficult to convert a
larger mass to another phase
• ,olarity• ,olar molecules have higher m.p. and b.p. than
nonpolar molecules of similar molecular mass due to
their stronger attractive force
n i c t r y Eelting and Boiling ,oints +
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F , r o p e
r t i e s B a s
e d o n ' l e c t r o n
r u c t u r e
a n d E o l e c u l a r e o m e t Eelting and Boiling ,oints
!elected Compounds by Bonding Type