Page 66 - Materials Science and Engineering An Introduction

38 • Chapter 2 / Atomic Structure and Interatomic Bonding

Figure 2.16 Schematic diagram that shows the
formation of sp hybrid orbitals in carbon. (a) 2p
2
Pro motion of a 2s electron to a 2p state; (b) this Energy 2s
promoted electron in a 2p state; (c) three 2sp orbitals (a)
2
that form by mixing the single 2s orbital with two 2p 1s
orbitals—the 2p z orbital remains unhybridized.
promotion
of electron

2p
2s
Energy
(b)
1s

sp 2
hybridization
2p
z
2sp 2
Energy
(c)
1s

Metallic Bonding
metallic bonding Metallic bonding, the final primary bonding type, is found in metals and their alloys. A rela-
tively simple model has been proposed that very nearly approximates the bonding scheme.
With this model, these valence electrons are not bound to any particular atom in the solid
and are more or less free to drift throughout the entire metal. They may be thought of as
belonging to the metal as a whole, or forming a “sea of electrons” or an “electron cloud.”
The remaining nonvalence electrons and atomic nuclei form what are called ion cores,
which possess a net positive charge equal in magnitude to the total valence electron charge

sp 2

120° C C
C
sp 2 sp 2

Figure 2.17
Schematic diagram C C
2
showing three sp
orbitals that are copla-
nar and point to the
corners of a triangle; the
angle between adjacent
orbitals is 120 . C C
(From J. E. Brady and F.
Senese, Chemistry: Matter
and Its Changes, 4th
edition. Reprinted with
permission of John Wiley Figure 2.18 The formation of a hexagon by the bond-
2
& Sons, Inc.) ing of six sp triangles to one another.