Molecular polarity Flashcards
(28 cards)
What makes a structure asymmetricla
Center is exposed OR there are atoms of different electonegativies bonding around the central atom
What types of intermolecular forces are there between neutral molecules
- London Dispersion (LDF)
- Dipole-Dipole forces (DD)
- Hydrogen bonding
How many electrons does boron take
6
# of atoms boded to central atom: 3 # of unshared electron pairs on central atom: 1
Trigonal pyramidal
# of atoms boded to central atom: 2 # of unshared electron pairs on central atom: 0
Linear
London dispersion forces (LDF)
- Atrraction caused by a temporary, uneqeual distribution of electrons, which cause a momentary positive/negative area on a molecule
- Made stronger by more electrons in the molecule
- Found in all atoms and molecules ( even noble gases)
What makes molecules stick together
Forces that exist between molecules called intermolecular forces
# of atoms boded to central atom: 1 # of unshared electron pairs on central atom: 1
Linear
# of atoms boded to central atom: 1 # of unshared electron pairs on central atom: 2
Linear
What makes a molecule polar
- It has polar bonds
2. It is asymmetrical (center is exposed or atoms of dif electronegativities bonded to center)
How do you mix substances
You need two substances with the same type/strength of IMF
EX: Only things with LDF dissolve/mix in things with only only LDF
-DD forces interact well with other DD forces (Hyrdogen bonding is a stong DD force)
What makes the central exposed
It has unshared electrons
How to tell difference in strength for DD
-HB the strongest. Otherwise whichever has greater electronegativity difference
# of atoms boded to central atom: 3 # of unshared electron pairs on central atom: 0
Trigonal planar
Exeptions to the 8 electron rule
B only takes 6 valence electrons
H only take 2 valence electrons (1 Bond)
# of atoms boded to central atom: 4 # of unshared electron pairs on central atom: 0
Tetraheda
Dipole-Dipole forces (DD)
- Attraction caused by permanently establish dipoles on molecules (the partial positive and partial negative charge)
- Found in polar molecules
- Stronger with a greater electronegativity difference
Hydrogen bonding
-Extremely stong dipole
-Found when hydrogen is bonded to N, O, or F directly
and it has unshared electrons
# of atoms boded to central atom: 2 # of unshared electron pairs on central atom: 2
Bent
What does strong IMF mean
- Higher boiling point
- Higher melting point
- Lower vapor pressure (less evaporation)
How many electrons does Barrilium take
4
# of atoms boded to central atom: 2 # of unshared electron pairs on central atom: 1
Bent
The stronger the IMF….
The more the molecules want to stick together
What is the substance mixing rule
-Like dissolves like
Polar dissolves polar, nonpolar dissolves nonpolar