Transcript Slide 1
Part of
MATERIALS SCIENCE
& A Learner’s Guide
ENGINEERING
AN INTRODUCTORY E-BOOK
Anandh Subramaniam & Kantesh Balani
Materials Science and Engineering (MSE)
Indian Institute of Technology, Kanpur- 208016
Email: [email protected], URL: home.iitk.ac.in/~anandh
http://home.iitk.ac.in/~anandh/E-book.htm
Ionicity of the chemical bond
Metallic, covalent and ionic bonds are extreme cases and often the nature of the
bonding is between these perfect scenarios
In the Covalent bond picture the electrons are equally shared by the participating
atomic species high electron density between nuclei
In the Ionic bond picture the electron is completely transferred to one of the
participating species high electron density around one of the nuclei
In the metallic bond picture the electron belongs to the solid as a whole
uniform electron density in the whole crystal
If one looks at the electron density midway between the nuclei:
NaCl → ~0.1 electron/Å3
C (diamond) → ~5.0 electron/Å3
The figure on the next slide gives a schematic representation of progress from a
covalent crystal to a ionic crystal
Covalent to Ionic crystals
Slightly ionic
Covalent Crystal
Increasing ionicity
To ‘ideal’ ionic
Ionic Crystal