2. Definitions
Bond: a type of interaction between atoms
that result in atoms staying close together
Molecule: two or more atoms held together
by a covalent bond
Intramolecular: forces of attraction within a
molecule (e.g. intramurals)
Intermolecular: forces of attraction between
molecules in a compound (e.g. international)
4. Intramolecular Bonds
Electronegativity: attraction of an atom for
electrons
Example of a very electronegative atom:
oxygen
When two atoms with different
electronegativity get together…
6. Intramolecular: Ionic
If two atoms with very large differences in
electronegativity get together, one of atom
could take away an electron from the other
Acceptor “stealer” of electron becomes
negativity charged (anion = negative ion)
Donor of electron becomes positively
charged (cation = positive ion)
7. Intramolecular: Ionic
Ionic bond forms from an attraction between
an anion and cation
Ionic compounds are formed by ionic bonds
Salts are ionic compounds (e.g. Na+ + Cl-
NaCl)
Salt crystals have a 3D lattice because of +/-
attractions
10. Intramolecular: Covalent
Covalent bond forms when atoms share electrons
Nonpolar covalent bond
atoms have the same electronegativity
electrons are equally shared
e.g. H2
Polar covalent bond
atoms have slight differences in electronegativity
electrons are unequally shared
e.g. HCl
12. Polarity of a Molecule
Polarity dependent on the polarity of the bond AND
the molecular SHAPE
Bond
Shape Nonpolar bond Polar bond
nonpolar nonpolar
Symmetrical molecule molecule
(e.g. H2) (e.g. CO2)
nonpolar polar molecule
Assymetrical
molecule (e.g. HCl, H2O)
18. Types of Interactions Summary
Intermolecul Intramolecul
ar ar
London Dipole- Hydrogen Covalent Ionic
(dispersion) dipole bonding &
forces Ion-dipole
Nonpolar Polar
Covalent Covalent
19. London Dispersion
Exists
between all
molecules
Weak force,
due to
instantaneous
diploes
20. Dipole-Dipole
Exists between
polar molecules
Due to permanent
dipoles
21. Hydrogen Bonding
Strong force (just a very strong dipole-dipole)
Between a polar molecule with an H-atom and a
polar molecule with an electronegative atom
(usually O, N or F)
22. Ion-Dipole
Ion-Dipole
Dipole is attracted to an oppositely charged ion
When ionic compounds dissolve in water, water
molecules surround the ion and remove it from the
crystal lattice structure (hydration shell)
23. Hydrophobic Interactions
Nonpolar molecules are
excluded from mixing with polar
molecules
Nonpolar molecules tend to
associate with each other
Can occur spontaneously (e.g.
oil molecules spontaneously
associate excluding water)
