1. Chapter 7 “Ionic and Metallic Bonding”

2. Section 7.3 - Bonding in Metals
OBJECTIVES:
I can model the valence electrons of metal atoms.
I can describe the arrangement of atoms in a metal.
I can explain the importance of alloys.

3. Metallic bonds are… How metal atoms are held together in a solid
Metals hold on to their valence electrons very ____________________
Why?
Think of metals as positive ions (_______________) floating in a sea of electrons

4. The sea-of-electrons model
Electrons are free to move through the solid, therefore…
Metals __________________________ +

5. Metals are malleable and ductile
Malleable: can be ___________________ or _____________________ into shapes
Ductile: can be ____________ into wires
Why? The sea-of-election model!
Drifting valence electrons insulate the __________________ from each other
Allows the cations to slide past one another easily

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

7. By contrast, ionic solids are brittle+ -
Strong repulsion _____________ a crystal apart
Why? + -
Force

8. Crystalline structure of metal
If made of one kind of atom, metals are among the simplest crystals; very _____________________ & orderly
Similar to stacking oranges at the grocery store
Further apart Closely packed

9. Alloys
We use lots of metals every day, but few are _________________ metals
Alloy: _____________________ of two or more elements, at least one of which is a metal
Made by melting a mixture of the ingredients, then cooling
Brass: an alloy of Cu and Zn
Bronze: Cu and Sn

10. Why use alloys?
Properties of alloys are often _________________ to the pure element
Sterling silver (92.5% Ag, 7.5% Cu) is ______________ and more _____________ than pure Ag, but still soft enough to make jewelry and tableware
Steels are very important alloys due to useful properties: corrosion resistance, ductility, hardness, toughness, cost