1. Polarity Notes

2. February 5, 2014 Students will be able to define and identify: – Bond polarity and overall molecular polarity – Intermolecular forces. Lewis/Polarity/IMF/Geometry Lab Video of the day: The Big Three – Methane Methane – Water – Ammonia

3. Introduction: Polarity Polarity is a concentration of charge on one side of a bond Some molecules have negative or positive poles, like magnets

4. Individual bond polarity Polarity is determined by electronegativity difference To draw individual bond polarity: – Compare: Only two atoms at a time – The more electronegative atom attracts electrons more – Draw arrow towards the more electronegative atom

5. http://www.youtube.com/watch?v=_ M9khs87xQ8

6. Review: Electronegativity Electronegativity is the measure of how well an atom in a bond attracts electrons Electronegativity increases up and right across the periodic table

7. Are there lone pairs on the center atom? Yes No Polar Are the peripheral (outer) atoms different? Yes No PolarNonpolar Overall Polarity

8. Bond Polarity Examples Cl 2 Cl has the same electronegativity as Cl. We cannot draw an arrow to show polarity. The molecule is nonpolar.

9. Polarity Examples CH 3 I C has a higher electronegativity than H. We draw arrows from each H towards C. I has a higher electronegativity than C. We draw an arrow from C towards I. There are no lone pairs around the central atom and the outer atoms are different. The molecule is POLAR.

10. Polarity Examples CH 2 O C has a higher electronegativity than H. We draw arrows from each H towards C. O has a higher electronegativity than C. We draw an arrow from C towards O. There are no lone pairs around the central atom and the outer atoms are different. The molecule is POLAR.

11. Polarity Examples O 3 O has the same electronegativity as O. We cannot draw arrows to show polarity. The central atom has a lone pair, so the molecule is polar.

12. Polarity Examples PF 3 F is more electronegative than P. We draw an arrow from P to each of the fluorine atoms. The central atom has a lone pair, so the molecule is polar.

13. Polarity Examples NH 4 + N is more electronegative than H. We draw an arrow from each H towards N. The central atom doesn’t have a lone pair, and the outer atoms are the same so the molecule is nonpolar.