5.3 Study Guide Flash Cards
What are London Dispersion forces?
They are the weakest intermolecular forces that are generated from temporary dipoles created when electrons in a molecule create instantaneous polar regions.
Are London Dispersion forces present in polar, nonpolar or both kinds of molecules?
Both
What are Dipole-Dipole interactions?
Intermolecular forces between molecules that are permanently polar.
What does it mean for a molecule to be polar?
One end of the molecule has a partial negative charge and the other end of the molecule has a partial positive charge.
What is a hydrogen bond?
An intermolecular force that occurs when a Hydrogen atom is bonded to a highly electronegative atom like Oxygen, Nitrogen or Florine experiences an attractive force to an electronegative atom in a nearby molecule.
List the three intermolecular forces in order from weakest to strongest.
- London Dispersion Forces 2. Dipole-Dipole Forces 3. Hydrogen Bonds
What does the structure of a polar molecule look like?
Asymmetrical with an uneven distribution of electron density due to different electronegative atoms
What does the structure of a nonpolar molecule look like?
Symmetrical with atoms containing similar electronegativity
What type of intermolecular interactions can nonpolar molecules have?
Only London Dispersion Forces
What determines the type of intermolecular interactions molecules can have?
Polarity - being polar or nonpolar determines the type of intermolecular interactions.
What type of interactions can polar molecules have?
London Dispersion Forces, Dipole-Dipole and Hydrogen Bonds
Are polar molecule soluble in water? Why?
Yes, the uneven electron density in polar molecules allows them to form hydrogen bonds with the water molecules
Are nonpolar molecules soluble in water? Why?
No, nonpolar molecules are insoluble in water. Nonpolar molecules have an even electron density that does not facilitate hydrogen bonding with water molecules.
Polar Covalent Bond definition
Bonding electrons shared unequally between two atoms
Nonpolar Covalent Bond definition
Bonding electrons shared equally between two atoms
Generally, the term polar means?
Opposite Ends
EN is an abbreviation for?
Electronegativity
The bigger the difference in EN the ———- the partial charges will be.
larger
The higher the EN of a molecule the more —— is it.
Polar (Higher pull and more assymetry)
An atom having a stronger EN in a molecule means?
That atom has a stronger pull on the shared electrons than the other atoms it is next to in the molecule.
The Carbon atom in Methane (CH4) is more electronegative than the Hydrogen atoms but the molecule is symmetrical. Is Methane polar or nonpolar?
Nonpolar, the electrons are pulled equally by Carbon from the four Hydrogen atoms causing the symmetrical scale and causing the molecule to not end up with more electrons on one end of the molecule.
The Nitrogen atom in Ammonia (NH4) is more electronegative than the Hydrogen atoms and the molecule is asymmetrical. Is Ammonia polar or nonpolar?
Polar, the share electrons are pulled more toward the Nitrogen atom and less toward the Hydrogen atoms giving the Nitrogen end a partial negative charge and the Hydrogen end a partial positive charge.
The difference in EN of Oxygen (3.5) and Hydrogen (2.1) is and Oxygen (3.5) and Sulfur (2.5) is? Which is more polar?
O-H EN = 1.4 and O-S EN = 1.0; O-H is more polar because the difference in EN is larger.
If a molecule has an O-H bond is it more soluble in water or oil?
Water
