Chapter
7
Chapter 4
Ionic and Metallic Bonding
Atoms and Chemical
Bonding
Valence Electrons
• Highest energy level
• Determine chemical properties
• [Ne]4s2 3d10 4p5 - Bromine
7 valence eRepresentative elements = group #
Valence Electrons
Lewis (1916)
1
2
3
4
5
6
Valence electrons are the electrons in the atom’s highest
numbered energy level.
7
8
Electron dot Structures
• Lewis dot
• Show electrons as dots
•
• Ca•
•B•
• Fill in each side with one dot before you double up
Octet Rule
In forming compounds
atoms gain, lose, or share
in such a way that they achieve the electron configuration of the
nearest noble gas in the periodic table.
Noble gases are stable
have eight electrons in the outermost level
Ionic Bonding
 Atoms lose or gain electrons to form ions
 Cations are positive ions
 metals generally form cations
 Anions are negative ions
 non-metals generally form anions
 Ionic compounds are held together by
electrostatics- the positive charge of the cation
attracting the negative charge of the anion.
Ionic Bonding Continued
Ionic Compound
 METAL + NONMETAL
 Important metal ions
 group 1A - loose 1 electron (+1)
 group 2A - loose 2 electrons (+2)
 group 3A - loose 3 electrons (+3)
 Important non-metal ions
 group 7A (-1), group 6A (-2), group 5A (-3)
Properties of Ionic bonds
• Most are crystalline solids at Room temp
Stable structures with all of the (+) and (-)
attractions
Properties cont.
Stable structures with all of the (+) and (-)
attractions
• High melting points
• Conduct electricity
– Ions move freely so e- can travel toward (+)
– When dissolved in water
Ionic Bonds
•
•
•
•
One cation and one anion
Electrically neutral
Cation gives eAnion takes e– Example Aluminum and bromine
Common Ions and Their
Position in the Periodic Table
Lewis Structures
• Al •
•Cl•
Cl
Cl
[Al] [Cl]3
Names of Common Nonmetallic
Ions
Polyatomic Ions
Polyatomic means “many-atom” ion
Metallic bonds
• Closely packed cations
• Valence e- are free and can drift from one
metal to another
• Meallic bonds consist of the attraction of
ther free-floating valence e- for the
positively charged metal ions
Metallic bonds (e-)
• they do not "belong" to any one atom
• are part of the whole metal crystal
• *Metallic bonds are best characterized by the
phrase "a sea of electrons"*
Metallic properties
• electrons flow explains characteristics of metals:
• - Metals are good conductors of heat and electricity.
– mobility of the electrons.
• - The "cement" effect of the electrons determines the
hardness Some
• - Metals are lustrous.
– due to the uniform way that the valence electrons absorb and reemit light energy.
• - Metals are malleable (can be flattened) and ductile (can
be drawn into wires)
– because the metal cations and electrons can "flow" around each
other, without breaking the crystal structure.
http://www.ithacasciencezone.com/chemzone/lessons/03bonding/mleebonding/metallicbonding.htm
Alloys
• Mixture of two or more elements, at least one is a
metal
• Example: brass = copper and zinc
• Properies are better than those of the single
elements
• Sterling silver = siler and copper
– Durable /no tarnish
Steel is a very important alloy
iron, carbon, boron, chromium, manganese, and more