Chem - IMFs & Definitions

Electronegativity

Ability of an atom to hold onto its electrons

Dipole

“2 poles”; a partial positive and a partial negative charge (an atom or molecule with a charge distribution)

Intermolecular force

electrostatic (attractive or repulsive forces) interactions between molecules

London Dispersion Forces

Electrostatic attraction due to instantaneous dipole that induces a dipole on a neighboring particle

Dipole-Dipole

Electrostatic attraction due to permanent dipole

• heteroatom must be present

Hydrogen Bonding

Electrostatic attraction due to H-donor and H-acceptor (NOT a bond)

• H-donor: H must be bonded to a heteroatom

• H-acceptor: heteroatom must have at least one pair of nonbonding electrons

Deciding the strength of a force:

1. How many H-bonds and how many carbons?

2. How electronegative is the dipole?

3. How much surface area?

4. Is there branching?

Boiling Point

amount of energy required to pull 2 molecules away from each other to overcome their IMF and transform from liquid to gas (is NOT breaking bonds)

Higher electronegativity —>

larger dipole —> higher SA contact —> stronger dipole-dipole attraction —> stronger IMF —> higher BP

Polar bond

the unequal sharing of electrons between two atoms (partial negative and partial positive charge because of difference of electronegativity)

Nonpolar bond

the equal sharing of electrons between two atoms (little to no difference in electronegativity)

Induced dipole

temporary distribution of electrons (electrons are sloshed to one side); must have a double bond

ion dipole

strongest molecular force

C-H bonds are nonpolar because…

they have similar electronegativity meaning an equal or near equal sharing of electrons

How are electronegativity and polarity related?

Electronegativity determines bond polarity; greater difference in electronegativity leads to a more polar bond