1. INTERATOMIC BONDS

2. INTERATOMIC BONDS
There different types of primary or chemical bond are found in solids:
Ionic bonding
Covalent bonding
Metallic bonding
Secondary or van der Waals bonding (physical forces)
Fluctuating induced dipole bonds
Polar molecule-induced dipole bonds
Permanent dipole bonds
Each of these 3 types of bonding arises from the tendency of the atoms to assume stable electron structures, like inert gases, to completely filling the outermost electron shell

3. - + IONIC BONDING • Occurs between + and - ions.
• Requires electron transfer.
• Large difference in electronegativity required.
• Example: NaCl
Na (metal)
unstable
Cl (nonmetal)
electron + -
Coulombic
Attraction
Na (cation)
stable
Cl (anion)

4. IONIC BONDING (con’t)
Fig 2.9 Schematic representation of ionic bonding in sodium chloride

5. IONIC BONDS: metal + nonmetal
donates accepts electrons electrons  
Dissimilar electronegativities  
ex: MgO Mg 1s2 2s2 2p6 3s O 1s2 2s2 2p4
[Ne] 3s2 
Mg2+ 1s2 2s2 2p O2- 1s2 2s2 2p6
[Ne] [Ne]

6. Source: https://youtu.be/dqW7H7c7M4A
IONIC BONDS
Source:

7. Examples: IONIC BONDING
• Predominant bonding in Ceramics
NaCl
MgO
Give up electrons
Acquire electrons
CaF 2
CsCl
Adapted from Fig. 2.7, Callister & Rethwisch 8e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University.

8. COVALENT BONDING similar electronegativity  share electrons
bonds determined by valence – s & p orbitals dominate bonding
Example: CH4
shared electrons
from carbon atom
from hydrogen
atoms H C CH 4
C: has 4 valence e-,
needs 4 more
H: has 1 valence e-,
needs 1 more
Electronegativities
are comparable.
Adapted from Fig. 2.10, Callister & Rethwisch 8e.

9. TWO EXAMPLES OF COVALENT BONDING
Diamond is very hard and has a very high melting temp. (3550 °C)

10. Source: https://youtu.be/ZxWmyZmwXtA
COVALENT BONDS
Source:

11. METALLIC BONDING
Sharing of outer shell electrons by all atoms to form a general electron cloud that permeates the entire block
Fig 2.11 Schematic illustration of metallic bonding

12. Source: https://youtu.be/vOuFTuvf4qk
METALLIC BONDS
Source:

13. SECONDARY BONDING
Whereas primary bonds involve atom‑to‑atom attractive forces, secondary bonds involve attraction forces between molecules
-No transfer or sharing of electrons
-Bonds are weaker than primary bonds
Arises from interaction between atomic or molecular dipoles
Fig 2.12 Schematic illustration of can der Waals bonding between two dipoles

14. PROPERTIES FROM BONDING: Tm
• Bond length, r
• Melting Temperature, Tm r o
Energy r
• Bond energy, Eo Eo =
“bond energy”
Energy r o
unstretched length
smaller Tm
larger Tm
Tm is larger if Eo is larger.

15. Properties From Bonding : a
• Coefficient of thermal expansion, a D L
length, o
unheated, T 1
heated, T 2
coeff. thermal expansion D L = a ( T - T ) 2 1 L o
• a ~ symmetric at ro r o
smaller a
larger a
Energy
unstretched length Eo
a is larger if Eo is smaller.