1. Metallic Bonds
2a. Students know atoms combine to form molecules by sharing electrons to form covalent or metallic bonds or by exchanging electrons to form ionic bonds.

2. What gives metals its metal properties?
Metallic Bonds
Metals conduct heat and electricity, are shiny, and deform rather than break under pressure (malleable/ductile).
They are useful to man.
What gives metals its metal properties?
The outer electrons of most metal atoms tend to be weakly held to the atomic nucleus.

3. Outer electrons of most metal atoms are easily displaced…
Outer electrons of most metal atoms are easily displaced….leaving behind positively charged metal ions.
The many electrons displaced from a large group of metal atoms flow freely through the resulting metal ions.

4. Sea of electrons creates electricity!
This “fluid” of negatively charged electrons holds the positively charged metal ions together in the type of chemical bond known as a metallic bond.
The mobility of electrons in a metal accounts for the metal’s significant ability to conduct electricity and heat; gives them their shiny, opaque quality; and allows them to be molded into various shapes.
Sea of electrons creates electricity!

5. Metal Properties Hammered into shape (bend).
Also ductile - drawn into wires.
Both malleability and ductility explained in terms of the mobility of the valence electrons

6. Due to the mobility of the valence electrons, metals have:
Notice that the ionic crystal breaks due to ion repulsion!
1) Ductility
2) Malleability
and

7. Malleable +
Force

8. Malleable + + + + Force + + + + + + + +
Mobile electrons allow atoms to slide by, sort of like ball bearings in oil. + + + +
Force + + + + + + + +

9. Ionic solids are brittle
Force + -

10. Ionic solids are brittle
Strong Repulsion breaks a crystal apart, due to similar ions being next to each other. + -
Force + - + - + -

11. Alloys We use lots of metals every day, but few are pure metals
Alloys are mixtures of 2 or more elements, at least 1 is a metal
made by melting a mixture of the ingredients, then cooling
Brass: an alloy of Cu and Zn
Bronze: Cu and Sn

12. Why use alloys? Properties are often superior to the pure element
Sterling silver (92.5% Ag, 7.5% Cu) is harder and more durable than pure Ag, but still soft enough to make jewelry and tableware
Steels are very important alloys
corrosion resistant, ductility, hardness, toughness, cost