Review Polar Covalent: unequal sharing of electrons (electronegativity difference >0.4) Nonpolar Covalent: equal sharing of electrons (electronegativity difference <0.4)

Polar Covalent Bond A Polar Covalent Bond is unequal sharing of electrons between two atoms (H-Cl) in an ASYMMETRICAL molecule In a polar covalent bond, one atom typically has a slight negative charge, and the other atom has a slight positive charge

Nonpolar Covalent Bond A Nonpolar Covalent Bond is an equal sharing of electrons between two atoms (Cl-Cl, N-N, O-O)

Classification of Bonds You can determine the type of bond between two atoms by calculating the difference in electronegativity values between the elements The bigger the electronegativity difference the more polar the bond. Type of Bond Electronegativity Difference Nonpolar Covalent 0  0.4 Polar Covalent 0.5  1.9

*Exception!!!!! If molecule is symmetrical it is NONPOLAR!

Summary In a polar bond, one atom is more electronegative than the other (>0.4 difference). In a nonpolar bond, both atoms have similar electronegativities (<0.4 difference). An asymmetric molecule with polar bonds is a polar molecule. An asymmetric molecule with nonpolar bonds is a nonpolar molecule. A symmetric molecule, regardless of the polarity of the bonds, is always a nonpolar molecule.

Practice-Polar/Nonpolar CO2 H2O BF3 NH3 CCl4

Polar/Nonpolar https://www.youtube.com/watch?v=PVL24HAesnc

INTRAmolecular Forces “Within” the molecule and are called covalent and ionic bonds.

INTERmolecular Forces Forces that occur between molecules. Intramolecular (ionic and covalent) bonds are stronger than intermolecular forces.

Khan Academy https://www.khanacademy.org/science/organic-chemistry/gen-chem-review/electronegativity-polarity/v/intermolecular-forces-and-molecular-bonds

How Strong? The higher the boiling point = stronger the IMFA

Intermolecular Forces Dipole-dipole Hydrogen bonding! Dipole-induced dipole London dispersion forces

12.6 Dipole–Dipole Attraction Polar molecules contain different atoms which have different electronegativity's and can be thought to be like a small bar magnet. Oppositely charged ends attract and like ends repel. Molecules organize themselves to maximize the attractive forces and minimize repulsive forces giving molecules unique shapes.

12.6 Hydrogen Bonding Strong dipole-dipole forces. Strongest intermolecular force Hydrogen is bound to a highly electronegative atom – nitrogen, oxygen, or fluorine. “FON”

Hydrogen Bonding in Water Blue dotted lines are the intermolecular forces between the water molecules.

12.6 Hydrogen Bonding Affects physical properties Boiling point

Dipole-Induced Dipole When a polar molecule gets near a non-polar one, it induces the non-polar one to become polar; thus, they connect

12.6 London Dispersion Forces Instantaneous dipole that occurs accidentally in a given atom induces a similar dipole in a neighboring atom. Significant in large atoms/molecules. Occurs in all molecules, including nonpolar ones. Weakest IMFA

12.6 London Dispersion Forces Become stronger as the sizes of atoms or molecules increase. Larger mass=stronger LDF=higher BP

CFU 1. Put the following intermolecular forces in order from strongest to weakest: Hydrogen bonding London dispersion forces Dipole-dipole Dipole-induced dipole 2. Which would have a higher BP: CH4 or C2H6? Why?

Draw LDDs for: BeH2 (no octet) PO43- BCl3 (no octet) SO2 - Is it POLAR or NONPOLAR? -IMFA a)1&2,b)3&4,c)1&3,d)2&3?

Draw LDDs & Predict Polarity: CF4 2) CO2 3) SeCl4 4) XeF4 - Is it POLAR or NONPOLAR? -IMFA a)1&2,b)3&4,c)1&3,d)2&3?