Transcript Chapter 7 Ionic and Metallic Bonding

CHAPTER 7
“IONIC AND METALLIC
BONDING”
VALENCE ELECTRONS ARE…?
 e-’s
responsible for chem props of
atoms
 in
s
outer energy level
and p e-’s in outer energy level
 Core e-’s – energy levels below.
ATOMS IN THE SAME COLUMN...
1)
2)

same outer e- configuration
same valence e-’s
valence e-’s easily determined

equal to group # for representative element

2A: Be, Mg, Ca, etc. have 2 valence e-’s
ELECTRON DOT DIAGRAMS…
valence e-’s
 symbol represents nucleus
& core e-’s
 Each side = orbital (s or p)
 dot = valence e- (8 max)
 don’t pair up until they
have to (Hund’s rule)

(px)
(py)
X
(pz)
(s)
Electron Dot diagram for
Nitrogen
 Nitrogen has 5 valence e write
 put
symbol
first 2 e- on rt side
 Add remaining e-’s CCW
N
The Octet Rule
Noble gases unreactive (Ch 6)
 Octet Rule: noble gas configuration
 8 outer level (stable)
 noble gas has 8 e-’s in outer level

(He
has 2)
FORMATION OF CATIONS
 Metals lose e-’s to attain a noble gas
configuration (NGC).
 They make + ions (cations)
 Na 1s22s22p63s1 1 valence e Na1+ 1s22s22p6 (NGC w/ 8 valence e-’s)
ELECTRON DOTS FOR CATIONS

Metals have few valence e-’s (usually 3 or
less); calcium has only 2 valence e-’s
Ca
ELECTRON DOTS FOR CATIONS
Metals few valence e-’s
 Metals lose

Ca
ELECTRON DOTS FOR CATIONS

Form + ions
2+
Ca
This is named the
“calcium ion”.
NO DOTS shown for cation
ELECTRON DOTS FOR CATIONS
Scandium
(21)
e- configuration is:
2
2
6
2
6
2
1
1s 2s 2p 3s 3p 4s 3d
lose 2e- (2+), or lose 3e- (3+)
2+
Sc
Sc =
3+
Sc = Sc
Sc Scandium (II) ion
Scandium (III) ion
ELECTRON DOTS FOR CATIONS
Silver (47)
Predicted configuration is:

1s22s22p63s23p64s23d104p65s24d9
Actual
configuration is:
1s22s22p63s23p64s23d104p65s14d10
Ag = Ag1+
(can’t lose any more,
charges of 3+ or greater are uncommon)
ELECTRON DOTS FOR CATIONS
Silver
did the best job it could, but
it did not achieve true NGC
“pseudo-noble gas
configuration”
ELECTRON CONFIGURATIONS: ANIONS
 Nonmetals
gain e-’s to attain NGC
 - ions (anions)
 S = 1s22s22p63s23p4 = 6 valence e S2- = 1s22s22p63s23p6 = NGC
 Halide ions - ions from halogens that
gain e-’s
ELECTRON DOTS FOR ANIONS
Nonmetals have many valence e-’s (usually
5+)
 gain e-’s

P
3(called “phosphide ion”, and
should show dots)
STABLE ELECTRON CONFIGURATIONS
All atoms react to achieve NGC
 Noble gases… s2p6
 8 valence e-’s (stable)

 octet
rule
Ar
Electron dot activity
Practice problems p. 193

1. Write the name and symbol of the ion
formed when
 A.
A sulfur atom gains two electrons
 B.
An aluminum atom loses three electrons
Practice problems p. 193

2. how many electrons are lost or gained in
forming each ion?
 A.
Ba2+
B. As3-
C. Cu2+
SECTION 7.2 IONIC BONDS AND IONIC
COMPOUNDS
 OBJECTIVES:
Explain
the electrical
charge of an ionic
compound.
SECTION 7.2 IONIC BONDS AND IONIC
COMPOUNDS
 OBJECTIVES:
Describe
three
properties of ionic
compounds.
IONIC BONDING
 Anions & cations – (+ and -)
 electrostatic
 Formula
forces
unit - simplest ratio of
elements in ionic cmpd
 bond thru transfer (lose/gain) of e-’s
 e-’s transferred to achieve NGC
IONIC BONDING
Na
Cl
metal (sodium) loses one valence eCl needs 1 e- for octet
Ionic Bonding 0:38
IONIC BONDING
dot & cross diagrams 2:57
+
Na
Cl
-
NOTE: NO DOTS shown for cation
IONIC BONDING
combining calcium and phosphorus:
Ca
P
All e-’s must be accounted for,
 each atom has NGC (stable)

IONIC BONDING
Ca
P
IONIC BONDING
2+
Ca
P
Ionic Bonding
2+
Ca
Ca
P
Ionic Bonding
2+
Ca
Ca
P
3-
Ionic Bonding
2+
Ca
P
Ca
P
3-
Ionic Bonding
2+
Ca
2+
Ca
P
P
3-
Ionic Bonding
Ca
2+
Ca
2+
Ca
P
P
3-
Ionic Bonding
2+
Ca
2+
Ca
2+
Ca
P
P
33-
Ionic Bonding
= Ca3P2
Formula Unit
chemical formula - shows kinds and
numbers of atoms in smallest representative
particle of substance.
Formula Unit - smallest representative
particle in ionic cmpd
Ionic bonds 6:28
PROPERTIES OF IONIC COMPOUNDS
1. Crystalline solids - regular repeating
arrangement of ions in the solid: Fig. 7.9,
page 197
 Ions strongly bonded
 Rigid structure
2. High melting points
Coordination number- # of ions of
opposite charge surrounding it
Chemistry of salt 6:23
- Page 198
Coordination Numbers:
Both the sodium
and chlorine have 6
NaCl
CsCl
TiO2
Maximizes contact
btwn opp charges
Both the cesium
and chlorine have 8
Each titanium has
6, and each oxygen
has 3
DO THEY CONDUCT?
3. Melted ionic cmpds conduct


Crystal structure breaks down
ions free to move (molten or aqueous)
SECTION 7.3
BONDING IN METALS
 OBJECTIVES:
Model
the valence
electrons of metal atoms.
SECTION 7.3
BONDING IN METALS
 OBJECTIVES:
Describe
the arrangement
of atoms in a metal.
SECTION 7.3
BONDING IN METALS
 OBJECTIVES:
Explain
alloys.
the importance of
METALLIC BONDS ARE…
 How
metal atoms are held together
in the solid.
 Metals hold on to their valence e-’s
weakly.
positive
ions (cations) floating in sea
of e-’s (Fig. 7.12, p.201)
SEA OF ELECTRONS
 e-’s
free to move thru solid.
 Metals conduct electricity
+
+ + +
+ + + +
+ + + +
METALS ARE MALLEABLE
Hammered
/ shaped
ductile - drawn into wires.
malleability & ductility explained
in terms of mobility of valence e-’s
- Page 201
Due to the mobility of the
valence electrons, metals have:
1) Ductility and 2) Malleability
Notice
that the
ionic
crystal
breaks
due to ion
repulsion!
MALLEABLE
Force
+
+ + +
+ + + +
+ + + +
MALLEABLE

Mobile e-’s allow atoms to slide by
 like
ball bearings in oil.
Force
+ + + +
+ + + +
+ + + +
IONIC SOLIDS ARE BRITTLE
Force
+
+
-
+
+
+
+
-
+
+
IONIC SOLIDS ARE BRITTLE

Strong Repulsion breaks crystal apart, b/c
similar ions next to each other.
Force
- + - +
+ - + - + - +
CRYSTALLINE STRUCTURE OF METAL
 Metals
are crystalline
Metals w/ 1 type of atom
simplest crystalline solid
Compact & orderly patterns
1. Body-centered cubic: Fig. 7.14 p.202:
every atom has 8 neighbors
(except atoms on surface)
Na,
K, Fe, Cr, W
CRYSTALLINE STRUCTURE OF METAL
2. Face-centered cubic:
every atom has 12 neighbors
Cu, Ag, Au, Al, Pb
3. Hexagonal close-packed
12 neighbors
different pattern due to hexagonal
Mg, Zn, Cd
ALLOYS
 We
use metals every day, few pure
metals
 Alloys made by melting a mixture of
ingredients, then cooling
 Brass: alloy of Cu and Zn
 Bronze: Cu and Sn
WHY USE ALLOYS?
Properties superior to pure element
 Sterling Ag (92.5% Ag, 7.5% Cu)

 harder
than pure Ag
 Soft enough for jewelry & tableware

Steels important
 corrosion
resistant, ductility, hardness,
toughness, cost efficient
MORE ABOUT ALLOYS…
 Table
7.3, p.203 – lists alloys
 Types:
 a)
substitutional alloy- atoms in components
are about same size
 b) interstitial alloy- atomic sizes differ;
 smaller
atoms fit in spaces btwn larger
 “Amalgam”-
dental fillings, contains
50%Hg, 22%Ag, 14%Sn, 8%Cu
Alchemy

Turning cheap metals into “gold”