Van der Waals forces are weak secondary bonds that occur between molecules due to momentary polarization caused by electron movement, dispersion effects, and hydrogen bridging. The arrangement of atoms in a material, whether in molecular, crystalline, or amorphous structures, has a significant effect on its properties. Metals have metallic bonding and solidify into lattice structures when cooled, with many metals exhibiting allotropic changes in crystal structure.

1. ELECTRICAL ENGINEERING
MATERIALS
MR. ASIF L. JAMADAR

2. SECONDARY BOND: VAN DER WAAL BONDING
 Weak or secondary bonds are known as Van der Waals forces.
 With secondary bonds, Molecules can be viewed as Electrical Dipoles
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 Momentary polarization caused by random movement of electrons
 Dispersion effect
 Hydrogen Bridge
 Such bonds has significant in biology system & engineering.

4. ATOM ARRANGEMENT IN MATERIALS
 Significant effect on its properties
 As manner of atomic grouping, the materials are classified as
 Molecular structures
 Crystal structures
 Amorphous structures
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5. CRYSTALLINE STRUCTURE OF METALS
 Metals are most important class of materials used in engineering application
 These materials have metallic bond.
 When metals solidify by cooling……
 Lattice form
 Iron is the example of allotropic change
 14 different crystal structures 5

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