Polarity and Intermolecular Forces
Electronegativity-ability of an atom to attract electrons
*Electronegativity of Common Elements increases up a group and across a period*
Electronegativity Difference
Bond Type
0 to 0.3
Nonpolar Covalent
0.4 to 1.6
Polar Covalent
≥ 1.7
Ionic
Nonpolar Covalent Bond- covalent bond with
electrons shared equally between the two atoms
Polar Covalent Bond- Covalent bond with greater
electron density around one of the two atoms
Ionic Bond-Bond with a positive ion and a negative ion
Intermolecular Forces- attractive forces between molecules
Dipole-Dipole Forces- attractive forces between polar molecules
Hydrogen Bond- a special dipole-dipole interaction
between hydrogen atoms in a polar N-H, O-H, or FH bond, and an electronegative N,O, or F atom
Ion-Dipole Forces- attractive forces between an ion and a
molecule
polar
Dispersion Forces- attractive forces that arise as a result of temporary dipoles induced in
atoms or molecules (Ion-induced dipole interaction, Dipole-induced
dipole interaction)
Van Der Waals/ London Dispersion Forces- attractive forces
between two nonpolar molecules (very weak)
Polarizability- ease with which the electron distribution in the atom or molecule can be
distributed
Strongest Intermolecular Forces to Weakest
Hydrogen Bond (H- N/O/F)
Dipole-Dipole (D-D) (2 polar)
Dipole-Induced Dipole (D-ID)
London Dispersion Forces (LDF)
*Note: Properties such as boiling point, viscosity, etc. increase with increasing strength of the
bond.*
Practice Problems
Show all work!
1. Given the electronegativity of Li is 1.0 and F is 4, what type of bond Lithium fluoride have?
What is the strongest intermolecular force on this compound?
2. Given the electronegativity of K is 0.8 and Cl is 3.0, what type of bond will potassium chloride
have? What is the strongest intermolecular force on this compound?
3. Given the electronegativity of C is 2.5 and N is 3.0, what type of bond will cyanide have?
What is the strongest intermolecular force on this compound?
4. Which of the following are capable of hydrogen bonding?(Circle One)
HI
BeH2
PF3
C3H8O3
5. Arrange the following in order of increasing boiling point: NaF, CO2, CH3OH, CH3Br
6.Which of the following molecules is(are) polar?
Cl2, CH4, CH2O, CH3Cl
Answer Key
1. Given the electronegativity of Li is 1.0 and F is 4, what type of bond Lithium fluoride have?
What is the strongest intermolecular force on this compound?
Ionic bond, Dipole-Dipole
2. Given the electronegativity of K is 0.8 and Cl is 3.0, what type of bond will potassium chloride
have? What is the strongest intermolecular force on this compound?
Ionic Bond, Dipole-Dipole
3. Given the electronegativity of C is 2.5 and N is 3.0, what type of bond will cyanide have?
What is the strongest intermolecular force on this compound?
Polar Covalent, Dipole-Dipole
4. Which of the following are capable of hydrogen bonding?(Circle One)
HI
BeH2
PF3
C3H8O3
5. Arrange the following in order of increasing boiling point: NaF, CO2, CH3OH, CH3Br
CO2 < CH3Br < CH3OH< NaF
6. Which of the following molecules is(are) polar?
CH3Cl, CH2O
Cl2, CH4, CH2O, CH3Cl