Material Science Engineering

Primary Bond

Formation of molecules

Ionic

Covalent

Metallic

Secondary Bonds

Attraction of molecules

Atoms

basic starting unit of element

Ion & molecule

ion-Charge Atom

molecule- 2 or more atoms bonded

Ionic

electrons transferred ( Ceramics/glass)

Covalent

Electrons shared (Semiconductors, polymers, ceramics)

Metallic

Electrons free to move(metals)

Ionic Bonding

One atom giving up an electron to another, resulting in attraction & bonding

Secondary bond

(Hydrogen bond > Dipole-dipole > London)

Weak attraction between atoms or molecules.

London -

Dipole-

Hydrogen -

Bond energy decreases → thermal expansion increases

Weaker bond → more thermal expansion
Stronger bond → less thermal expansion

Amorphous

not tightly packed ( Non crystallized ). Non organized arrangement of atoms

Monomers

Polymers

Monomers-small building block of polymers. For ex: Beads

Polymers- many monomers joined;crystalline. For Ex: Necklace

Bcc n=?

n=2

FCC n=?

n=4

HCP n=?

n=6

Xrays use to determine crystal structure

Material is fine powder being reflecting from various dense reflecting planes.

Isotropic

same properties in all directions

Anisotropic

different properties depending on directions

Why do coulombic forces remain stable

Forces attraction between like and unlike elements result to an equilibrium bond distance.