Chapter 7 “Ionic and Metallic Bonding”

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.

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

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

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

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

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

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

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

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