Chemical interaction

1. Some Foundations of Inorganic Chemistry
Part 2
Assoc. Prof. Dr. Pham Chien Thang
Department of Inorganic Chemistry

2. Outline
1. Overview of chemical interaction
2. Intramolecular interactions
3. Intermolecular interactions
4. Chemical interactions & Physical Properties
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3. Chemical interactions
• Chemical interactions: actions occur when two or more chemical
objects (atoms, ions, molecules) have an effect on one another.
• Determine physical & chemical properties of particular chemical
systems.
• One of most popular classification:
 Intra-molecular interactions (intra ~ inside)
 Inter-molecular interactions (inter ~ among/between)
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4. Electronegativity
• Electronegativity (χ): power of an atom in a molecule to attract electrons
to itself.
• Different scales for electronegativity
• Most common Pauling scale
χ(F) = 4.0 χ(O) = 3.4 χ(Cl) = 3.2 χ(N) = 3.0
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5. Outline
1. Overview of chemical interaction
2. Intramolecular interactions
3. Intermolecular interactions
4. Chemical interactions & Physical Properties
5

6. Intramolecular Interactions
• Interactions binds together atoms making up a molecule or a
compound -----> intramolecular interactions ~ chemical bonds.
• Classification:
Ionic bonds
Covalent bonds
Metallic bonds
• Characteristic of bonds depends on properties of the constitutent
atoms, particularly electronegativity.
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7. Ionic bond
• Ionic bond: formed between a positive ion & a negative ion by
electrostatic force
• Result from combintaion of atoms with large electronegativity difference
(metal & non-metal)
• Example:
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8. Covalent bond
• Covalent bond: formed by shared electrons between two atoms
• Result of the combintaion of two non-metallic atoms
• 2 types of covalent bond:
Non-plar covalent bond: electrons are evenly shared
Polar covalent bond: electrons are found around more
electronegative atoms -----> molecular dipole
• Example:
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9. Metallic bond
• Metallic bond: rises from electrostatic attraction between metal cations &
'sea' of delocalised electrons from the outer shells of initial metal atoms.
• Formed within pure metal or metal alloy
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10. Metallic bond
• Account for most of physical properties of metals (strength, ductility,
thermal & electric conductivity, optical ...)
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Malleable &
Ductile
Thermal
conductivity
Electrical
conductivity
force
applied

11. Intramolecular Interactions – Summary
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Interaction Model Basis of attraction Energy
(kJ/mol)
Example
Ionic bond Cation-Anion 400 - 4000 NaCl
Covalent
bond
Nuclei-shared electron
pair(s)
150 - 1100 H2
Metallic bond
Cations-delocalized
electrons
75 - 1000 Fe

12. Outline
1. Overview of chemical interaction
2. Intramolecular interactions
3. Intermolecular interactions
4. Chemical interactions & Physical Properties
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13. • Interactions between molecules & other neighboring particles
• Weaker than intramolecular interactions
• Classification:
 Hydrogen bond
 Ion-Dipole interaction
 Ion-Induced dipole interaction
 Dipole-Dipole interaction
 Dipole-Induced dipole interaction
 Oscilating dipole-Induce dipole interaction
Intermolecular interactions
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van der Waals
interactions

14. Hydrogen bond
• Partially electrostatic attraction between a H atom bonded to a highly
electronegative atom & an adjacent electronegative atom bearing lone
pair of electrons
• Example:
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H bond acceptor
H bond donor
O
O H
δ-
δ-

15. Molecular dipole
• Electric dipole: separation of positive & negative charge -----> dipole
moment
• Bond dipole moment: in a heteroatomic covalent bond,
 more electronegative atom partial – charge (δ–)
 less electronegative atom partial + charge (δ+)
-----> polar covalent bond with bond dipole moment
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16. Molecular dipole
• Molecular dipole moment: overall dipole moment of all polar bonds in
molecule
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No net dipole moment
NON-PLAR
Net dipole moment
POLAR

17. Molecular dipole
• Permanent dipole: molecule with net molecular dipole moment or polar
molecule
• Induced dipole: polarization of electron cloud of nonpolar molecules by
ions/permanent dipole
• Oscillating dipole: due to random oscillation of electron density in an
electron cloud
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vibration

18. Ion-Dipole interaction
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• Ion-Dipole interaction: electrostatic attraction between an ion & a
permanent molecular dipole
• Example:

19. • Ion-Induced Dipole interaction: electrostatic attraction between an ion &
an induced dipole caused by the ion.
• Example:
Ion-Induced Dipole interaction
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Cl– Cl–
δ–
δ+
Na+
Na+
δ– δ+

20. Dipole-Dipole interaction
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• Dipole-Dipole interaction (Keesom interaction): electrostatic interaction
between two permanent molecular dipole
• Example:
I
I

21. Dipole-Induced Dipole interaction
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• Ion-Induced Dipole interaction (Debey interaction): electrostatic
interaction between a permanent dipole & an induced dipole caused by
the permanent dipole
• Example

22. Oscillating Dipole-Induced Dipole interaction
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• Oscillating Dipole-Induced Dipole interaction (London dispersion
interaction): electrostatic interaction between an oscillating dipole & an
induced dipole caused by the oscillating dipole
• Universal interaction
• Example:
Oscillating
dipole
Oscillating
dipole
Induced
dipole

23. Intermolecular Interactions – Summary
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Interaction Model Basis of attraction
Energy
(kJ/mol)
Example
Ion–Dipole Ion charge-dipole charge 40 - 600 Na+...OH2
H bond
Polar bond to H-dipole
charge (high χ of F, O, N)
10 - 40 HF...HF
Dipole–Dipole Dipole charges 5 - 25 ICl...ICl
Ion–Induced
Dipole
Ion charge-Polarizable e–
cloud
3 - 15 Fe2+...O2
Dipole–
Induced Dipole
Dipole charge-Polarizable e–
cloud
2 - 10 H2O...O2
London
Dispersion
Polarizable e– clouds 0.05 - 40 I2
...I2

24. Outline
1. Overview of chemical interaction
2. Intramolecular interactions
3. Intermolecular interactions
4. Chemical interactions & Physical Properties
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25. Chemical Interactions & Physical Properties
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Substance Basis of attraction M.p &
B.p
State at
r.t.p
Solubility
Ionic
compounds
Strong electrostatic force
(cations – anions)
High Solid Often soluble in polar
solvents
Metals &
Alloys
Strong electrostatic force
(metal cations –
delocalised electrons)
High Solid
(except
Hg(l))
Insoluble in any solvents
Giant
Covalent
substances
Strong covalent bonds High Solid Insoluble in any solvents
Simple
Covalent
substances
Weak intermolecular
interactions
Usually
low
Usually
liquid/
gas
Polar solute – Polar solvent
Non-polar solute – Non-polar
solvent

26. Chemical Interactions & & Physical Properties
• Boiling point of simple covalent substances
• Important intramolecular interactions:
 Dipole-Dipole interaction (polar molecules)
 London dispersion interaction (non-polar molecules)
 Hydrogen bond
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27. Chemical Interactions & & Physical Properties
• Boiling point of simple covalent substances
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28. Chemical Interactions & & Physical Properties
• Boiling point of simple covalent substances
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