Intermolecular Forces Flashcards
(11 cards)
Intermolecular forces
Weak forces between molecules. Caused by attractive forces between very small dipoles
- permanent dipole-dipole
-van der waal
-hydrogen bonds
requiers energy , drawn as //// or IIII between molecules
Intramolecular forces
Forces between atoms
-covalent bonds
-ionic bonds
Very strong
Dipole
någonting med två olika laddningar, tex en molekyl som H20
Instantaneous Dipole-induced Dipole
Van der Waal bond.
When an instanteneous dipole induces/causes another dipole in another molecule.
The e- move to one side => slight charge => slight intermolecular force (causes the e- on the other molecule to be repelled -> dipole)
Very weak because e- move around all the time, which also causes it to happen in all molecules.
The amount e- determine strength of van der waal (more= stronger)
Boiling Points
When boiling something you area breaking intermolecular forces (so it can become fristående, gass)
Hydrogen Bonds
Strongest intermolecular bond
Formed by attraction betweeen δ+ & δ- / highly electronegative atoms
Occurs in O-H, N-H and sometimes F-H bonds
tex water: becuase there are lone pairs with δ- charge there becomes an atomic charge between H and O due to H being δ+ (H could become neutral with the O lone pair)
Determining IMF
- Identify type of substance
- only molecular compound → IMF - Check for polarity
- non polar → vdw
- polar →Dipole-Dipole & vdw & possible H-bonding - Check for Hydrogen bonding
- check if has a hydrogen atom directly bonded to N,O,F
-check if has a lone pair on N,O,F nearby - Consider special cases
- ions + polar →ion-dipole forces
-Larger Molecules (even non-polar) → stronger vdw pga more e-
non polar
van der waal
polar
Dipole-Dipole + vdw + possibly H-bonding
H bonded to N,O,F
Hydrogen bond + dipole-dipole + vdw
ionic + polar solvent
ion-dipole forces
