Atomic Theory 3: Intra and Inter molecular forced Flashcards
What are intramolecular forces
Intramolecular forces describe the chemical bonds within molecules
3 types of bonds
Ionic: complete transfer of e-
Covalent: equal sharing of e-
Polar covalent: unequal distribution of e- density, produces dipole
What is symmetrical distribution
Electron density is equally distributed bc EN is the same for both atoms in a covalent bond
Polar molecule
The more polar a molecule is (bigger EN difference) the more attractive it is to other polar molecules
Non polar covalent bonds
Has no polar bonds or has polar bonds but is symmetrical
Hydrophobic vs hydrophilic
Polar molecules are hydrophilic and non-polar molecules are hydrophobic.
Polarity of solvents
Water: polar
Oil: nonpolar
Alcohols: polar
What are intermolecular forces (Van der Waals)
The attractive forces between molecules and between ions and molecules. They are dependent on electrostatic attraction and are weaker than ionic/covalent bonds/
How can a substance exist as a liquid or solid
The molecules must be close together. There much be intermolecular attractive forces between the molecules.
What are London forces
Weak attractive forces between nonpolar molecules. Depends on the probability distribution of e-. Is always present but significant only when no other forces are present. Can produce a temporary dipole on a nearby atom, which breaks apart soon after. + e- = + london forces.
MP and BP of london forces
Least amount of electrons = weaker longdon force = lower melting and boiling point. Higher london force = higher MP and BP.
What are Dipole-Dipole forces
Attraction between polar molecules with permanant dipoles, are much stronger than london forces. Partial charges cause electrostatic attraction between opposite charges of other molecules
MP and BP of dipole-dipole forces
Higher melting and boiling point than london forces bc more energy is needed to overcome attractions. HCl is a dipole-dipole bond.
What are Hydrogen bonds
Attraction between H covalently bonded to N, O, or F
How do hydrogen bonds work
H bonds = strongest type of dipole-dipole attraction
N, F, O are highly electronegative bc of nuclear charge and small size
Electrons are withdrawn from H, giving it positive pole
