BONDING FORCES

1
BONDING FORCES ENERGIES

• Forces acting on atoms depends on their
  interatomic separation distance between 2
  nuclei of 2 atoms
• Attractive Forces (FA)
• Repulsive Forces (FR)

FN FA FR
r intertomic radius (see Fig. 2.8)
Cl-
Na
r
2
Figure 2.8
Cl-
Na
At equilibrium, FN FA FR 0 (no net force)
At equilibrium, r ro equilibrium spacing
A
B
C
D
Eo bonding energy of two atoms E required to
separate these two atoms to an infinite separation
At equilibrium (at equillibrium spacing) EN
EA ER is at a min. or EN Eo
3
BONDING FORCES
Referring to Fig. 2.8 (top)

• A _at_ high interatomic spacing (right side of
  curve)
• Little FA
• No FR (zero)
• B as interatomic spacing decreases (get
  closer move to left part of curve)
• FA increases
• FR increases
• C interatomic spacing reaches an EQUILIBRIUM
  (dashed line)
• r r0
• FN FA FR 0
• D If atoms try to move much closer (r ltlt ro)
• FR increases dramatically to prevent this.

Interatomic spacing decreases
4
BONDING ENERGIES
Referring to Fig. 2.8 (bottom)

• Energy between 2 atoms also depends on
  interatomic separation

EA attractive E ER repulsive E EN net E
EA ER

• As two atoms get closer EA and ER increase
• At r ro ? EN reaches a minimum (this is Eo)
• E0 bonding E of the two atom
• E0 is the minimum EN
• E0 is the E required to separate these 2 atoms
  to infinite separation

5
f09_02_pg27
IONIC
COVALENT
METALLIC
6
f07_02_pg24
Electronegativity Values (Fig. 2.7)
Table 12.1
7
What do Spider-Man and polyethylene (PE) have in
common?
8
Adhesion to wall not due to glue It is a dry
adhesion Explain
Spider Foot
Gecko Foot