3.1-3.3 Quiz Flashcards
London Dispersion Forces(LDFs)
- Definition
- What type of substances have LDFs?
- The result of Coulombic interactions between temporary, fluctuating dipoles.
- All substances have LDFs. They are the only force in nonpolar molecules or single nonmetal atoms.
What is the strongest IMF between large molecules?
LDFs
How does the polarizability of a molecule increase and why?
The polarizability of a molecule increases when the number of electrons in a molecule increases because larger atoms have more loosely held electrons in contrast to smaller atoms with tightly bound electrons.
Dipole-dipole interactions
- When do they occur?
- What substances have dipole-dipole?
- How do they increase?
- They occur between polar molecules.
- All polar molecules have dipole-dipole.
- When the difference in electronegativity is greater then the dipole is stronger
Are polar molecule interactions greater than nonpolar molecule interactions? Why or why not?
Yes because polar molecule interactions act in addition to LDFs.
Hydrogen bonding
- Where does it exist?
- It exists when hydrogen atoms bond to Nitrogen, Oxygen, or Fluorine in polar molecules. The positive end of NOF attracts to the negative end of H. The bond has to occur between molecules not within them.
Ion-dipole interactions
- When do they occur?
- What is the strength of these compared to other interactions?
- How do these increase?
- Present between ions and polar molecules
-They are stronger than dipole-dipole forces. - The strength increases with large charges and smaller ions and more polar molecules.
Intermolecular forces vs intramolecular forces
Inter- between molecules(H2 —- H2)
Intra- between atoms( H- - - O - H—-O)( dotted lines)
Weakest to strongest IMFs
Molecular(LDFs, Dipole-Dipole, Hydrogen Bonding), Ionic/Metallic, Covalent Network
Ionic interactions
- In what substances do these occur?
- When are ionic bonds stronger?
- When metals bond with nonmetals when they lose or gain electrons to form ions.
- They are stronger when the charges are larger and the ions are smaller.
Metallic interactions
- In what substances do these occur?
- Why do these occur?
- How do these increase?
- Only metal atoms
- These occur because multiple metallic cations are attracted to a delocalized sea of valence electrons.
- When there are smaller metallic cations and when there are more valence electrons.
Covalent network
- Name the atoms that will have a covalent network.
- How do these increase?
- (ATOMS WITH C ONLY OR SILICON) C(diamond), C(graphite), C60, SiO2, SiC
- When there are more covalent bonds formed(two nonmetals)
Polarizability
The ability of an atom to form a temporary or induced dipole
When going down the list of halogens they change in state from gas to liquid to solid. Why does this happen?
This is because the LDFs increase and the LDFs increase due to the increase in electrons. Also, larger molecules will have stronger LDF because the increase in electrons increases their polarizability.
Name the way LDFs increase.
They increase with increasing contact area(meaning the bigger it is(more electrons it has)) between molecules and with increasing polarizability of the molecules. Also, long thin molecules have more surface area, stronger LDFs, and stronger polarizability. Short round molecules have less surface area, weaker LDFs, and weaker polarizability. Lastly, the presence of double or triple bonds.
