Aim: How Can I identify a polar molecule from a non-polar molecule ?? *** Do-Now: What type of bond do the following compound have Use electronegativity differences between the elements as your reasoning. What type of bond does….. F2 CF CH3 HCl

How to show a bond is polar Isn’t a whole charge just a partial charge d+ means a partially positive (less electronegative) d- means a partially negative (more electronegative) The Cl pulls harder on the electrons The electrons spend more time near the Cl d+ d- H Cl

Polar Molecules Molecules with a positive and a negative end Requires two things to be true The molecule must contain polar bonds This can be determined from differences in electronegativity. Asymmetric molecule.

Symmetrical Molecules Because of symmetry, molecules that have polar bonds are overall a nonpolar molecules (+ and – charges cancel out or balance out) Examples: CO2 BF3 CCl4

Asymmetrical Molecules If a molecule has polar bonds (and there is no symmetry to cancel out + and – charges), the molecule is polar. Examples: H2O HCl NH3

Check for Understanding # 1 ***** Everyone Writes: List 5 differences between polar and non-polar molecules in your notebook. ( 3 minutes)

Dipole When there is unequal sharing of electrons a dipole exists Dipole is a molecule that has two poles or regions with opposite charges A dipole is represented by a dipole arrow pointing towards the more negative end

Dipole **Turn+ Talk= Take 1 minute to turn and talk to your elbow partner, Based on the image, what kind of molecules will Co2 and H20 be, make sure to use reasoning to explain your answer.

Do-now: Practice Drawing Dipoles Aim: How Can We Practice Writing Dipole Moments and identify polar and non-polar molecules? Do-now: Practice Drawing Dipoles HW: Practice Test Online due 12/5/16 P- Br P = 2.1 Br = 2.8 P –Br + - Remember to write down positive Atom first, the one with the lower Electronegativity is the positive one! Practice H(2.1) – S(2.5) F(4.0) - C(2.5) C(2.5) - Si(1.8) N(3.0) – O(3.5)

H –S + - C-F + - SI –C + - N–O + -

Is it a Polar or non-Polar molecule? HF H2O NH3 CF4 CO2 Polar molecule Polar Molecule

Answers

CF4 Non-Polar Molecule

Non Polar Molecule

Summary In a polar bond, one atom is more electronegative than the other. In a nonpolar bond, both atoms have similar electronegativities. 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.