Section 8 4 Metallic Bonds and Properties of

Section 8. 4 Metallic Bonds and Properties of Metals

Objectives l Describe a metallic bond l Explain the physical properties of metals in terms of metallic bonds l Define and describe alloys

Key Terms l Electron sea model l Delocalized electrons l Metallic bond l Alloy

Metallic Bonds l Metals do not bond ionically with other metals l Metals form a crystal lattice similar to an ionic compound. l. In the lattice the outer energy levels of the atoms overlap

Electron Sea Model l. All the metal atoms in a metallic solid contribute their valence electrons to form a ‘sea’ of electrons

Delocalized Electrons l These valence electrons are not held by a specific atom and can move freely from atom to atom

Metallic Bond l Metals with wandering electrons become cations l The cations are attracted to the other atom’s delocalized electrons l. This attraction is called a metallic bond

Properties of Metals l Metals are good conductors of heat or electricity l The delocalized electrons in a metal easily carry the heat or electricity through the metal l The delocalized electrons in metals also absorb and release electrons when exposed to light, giving metals their shiny luster.

Metal Alloys l An alloy is a mixture of elements that have metallic properties l. Because of the nature of the metallic bond it is relatively easy to introduce other elements into the metallic crystal

2 Types of Metal Alloys 1. Substitutional alloy -replaces metal atoms with atoms of similar size l. Ex: copper atoms replace silver atoms in sterling silver 2. Interstitial alloy -fills in the gaps between metal atoms with smaller atoms l. Ex: carbon atoms fill in the gaps between iron atoms in carbon steel

Homework l. P. 231 #40 -45 l. P. 237 #80 -82, 84