Warm Up:Warm Up:

Octet RuleOctet Rule

a filled layer contains 8 electronsa filled layer contains 8 electrons Exceptions (After bonding…)Exceptions (After bonding…)

H and He will have 2 H and He will have 2 Beryllium will have 4Beryllium will have 4 Boron will have 6Boron will have 6 Some transition metals can have more than Some transition metals can have more than

88

Dot Diagrams for Dot Diagrams for MoleculesMolecules

Atom with most unshared electrons goes in Atom with most unshared electrons goes in middle *capable of forming most bonds*middle *capable of forming most bonds*

Count to make sure you have the right number Count to make sure you have the right number of electronsof electrons

Each atom wants to have a full valenceEach atom wants to have a full valence Try these…Try these… CHCH4 4 OO2 2 COCO22

NHNH3 3 NN2 2 HH22OO

Domains

Write the shapes of each of Write the shapes of each of the dot diagrams you made the dot diagrams you made beforebefore

Warm Up: Label the Warm Up: Label the following bonds as polar following bonds as polar and nonpolar.and nonpolar.

BrBr22

HClHCl HH22

CHCH44

NHNH33

Molecular PolarityMolecular Polarity

DipoleDipole

Molecule with an overall unequal Molecule with an overall unequal distribution of electronsdistribution of electrons

Two atom moleculesTwo atom molecules

If the bond is non-polar, so is the If the bond is non-polar, so is the moleculemolecule

If the bond is polar, the molecule has a If the bond is polar, the molecule has a dipole and is polardipole and is polar

Do these molecules have Do these molecules have dipoles?dipoles?

NN22

OO22

COCO HFHF

Three atom moleculesThree atom molecules

If the 2 polar effects are equal and If the 2 polar effects are equal and oppositely directed, the molecule is oppositely directed, the molecule is nonpolarnonpolar

Otherwise, the molecule is polarOtherwise, the molecule is polar

Carbon dioxide water

Four atom moleculesFour atom molecules

It is possible that the 3 polar effects may It is possible that the 3 polar effects may cancel and produce a nonpolar moleculecancel and produce a nonpolar molecule

It is also possible that they don’t cancel It is also possible that they don’t cancel and produce a polar moleculeand produce a polar molecule

Exception to octet ruleNH3 (ammonia)

Five atom moleculesFive atom molecules

It is possible that the 4 polar effects may It is possible that the 4 polar effects may cancel and produce a nonpolar moleculecancel and produce a nonpolar molecule

It is also possible that they don’t cancel It is also possible that they don’t cancel and produce a polar moleculeand produce a polar molecule

CH3Cl

CH4

Intermolecular ForcesIntermolecular Forces

Between moleculesBetween molecules Dipole-dipoleDipole-dipole Hydrogen bondingHydrogen bonding Van der WaalsVan der Waals

Dipole-DipoleDipole-Dipole

Like electrical charges and magnets, Like electrical charges and magnets, dipoles can attract one anotherdipoles can attract one another Stronger attractions with stronger dipolesStronger attractions with stronger dipoles Stronger attractions when molecules are Stronger attractions when molecules are

closer together with lower temperature and closer together with lower temperature and higher pressurehigher pressure

Hydrogen BondingHydrogen Bonding

Occurs when Occurs when Hydrogen and Hydrogen and Fluorine, Oxygen, or Fluorine, Oxygen, or Nitrogen are presentNitrogen are present FONFON Ammonia, hydroflouric Ammonia, hydroflouric

acid, wateracid, water Higher boiling points Higher boiling points

with hydrogen bondingwith hydrogen bonding

Van der waalsVan der waals

Recall that electrons have a little bit of freedom Recall that electrons have a little bit of freedom to move around their electron cloudsto move around their electron clouds

VDW are produced by momentary uneven VDW are produced by momentary uneven electron distributionselectron distributions

Extremely weakExtremely weak Responsible for bonding of nonpolar Responsible for bonding of nonpolar

molecules, liquefaction of inert gases, 3 molecules, liquefaction of inert gases, 3 phases of halogens at STPphases of halogens at STP

Stronger for molecules with more electronsStronger for molecules with more electrons Gets stronger as molecules get closerGets stronger as molecules get closer

bromine