1. Chapter 8 Metallic Bonding
Chemistry, The Central Science, 10th edition
Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Chapter 8 Metallic Bonding
John D. Bookstaver
St. Charles Community College
St. Peters, MO
 2006, Prentice Hall, Inc. 1

2. Chemical Bonds
Strong electrostatic forces of attraction holding atoms together
Three basic types of bonds:
Ionic
Electrostatic attraction between ions
Covalent
Sharing of electrons
Metallic
Metal atoms bonded to several other atoms 2

3. Physical Properties of Metals
Conduct heat and electricity.
Malleable (can be pressed or hammered into sheets).
Ductile (can be drawn into wire).
Atoms can slip past each other.
So metals aren’t as brittle as other solids. 3

4. Electron-Sea Model
Metals can be thought of as cations suspended in a “sea” of valence electrons.
Attractions hold electrons near cations, but not so tightly as to impede their flow. 4

5. Electron-Sea Model
Metallic bonding is represented as an array of positive metal ions with valence electrons drawn among them as if the electrons were moving
Valence electrons from the metal atoms are considered to be delocalized and not associated with any individual atoms 5

6. Electron-Sea Model This explains properties of metals—
Conductivity of heat and electricity
Delocalized electrons are free to move and transfer electrical charge or energy
Malleability & Ductility
Deforming the solid does not change the environment immediately surrounding each metal core
Low volatility
Not capable of readily changing from a solid or liquid form to a vapor
Has a high boiling point
Deformation
Since malleable and ductile it can deform without breaking 6

7. Metallic Bonding Can be pure substances (made of only one metal)
alloys (mixtures of elements that have properties characteristic of metals)

8. Alloys Remember solutions can be mixtures of two or more metals Alloys
Blend of elements (at least one metal) prepared by mixing molten constituents and cooling them to produce a solid with metallic properties
Components of alloys are dispersed uniformly
Homogenous mixture
Two types of alloys
Substitutional
Interstitial 8

9. Substitutional Alloys
solute particles take place of solvent metal atoms
From between atoms of comparable radius
Solute atom substitutes for the other solvent atom for the other in the metal lattice

10. Properties of Substitutional Alloys
Density
Since solute atoms are replacing solvent atoms, the density of the alloy is between the densities of the two component atoms
Example: brass
Substitutional alloy of copper with the solute zinc
Malleability & Ductility
Less malleable and ductile than pure metals since the lattice is more rigid

11. Interstitial Alloys
Form between atoms of different radius, where the smaller atoms fill the interstitial spaces (gaps) between the larger atoms 11

12. Properties of Interstitial Alloys
Example:
Steel: carbon occupies the interstices in iron
Interstitial atoms make the lattice more rigid
Decreasing the malleability and ductility