1. 6.2 Covalent Bonding 6.2 Continued…Polar Bonds! Key Concepts What happens when atoms don’t share electrons equally? What factors determine whether a molecule is polar? How do attractions between polar molecules compare to attractions between nonpolar molecules?

2. 6.2 Covalent Bonding In general, atoms on the _______ side of the table have a greater attraction for electrons _____________ is the most electronegative element Why are the noble gases crossed off? right fluorine Their outer energy levels are full

3. 6.2 Covalent Bonding Because some atoms are better at attracting electrons than others, sometimes electrons are shared _________________ Unequal Sharing of Electrons HCl HCl In hydrogen chloride, which atom looks like it has more electrons around it? These atoms acquire ____________ charges unequally chlorine partial δ –δ +

4. 6.2 Covalent Bonding When atoms share electrons ________________, the covalent bond is called a ______________ covalent bonds Unequal Sharing of Electrons HCl HCl Polar means “opposite” in character δ – δ + unequally polar

5. 6.2 Covalent Bonding This is similar to the polar bear and the penguin…who has the ice cream more often? Unequal Sharing of Electrons HCl HClδ – δ + The polar bear (chlorine)

6. 6.2 Covalent Bonding If this was an ionic bond, how would the picture be different? Unequal Sharing of Electrons The penguin would GIVE AWAY the ice cream No sharing!

7. 6.2 Covalent Bonding Bond types can be determined by calculating the ______________ in the bonded atom’s electronegativity values Nonpolar covalent less than 0.5 Polar covalent 0.5 to 2.0 Ionic greater than 2.0 Electronegativity Table difference

8. 6.2 Covalent Bonding What type of bond is H – H ? Nonpolar covalent less than 0.5 Polar covalent 0.5 to 2.0 Ionic greater than 2.0 Electronegativity Table 2.1 – 2.1 = 0 nonpolar covalent

9. 6.2 Covalent Bonding What type of bond is C – O ? Nonpolar covalent less than 0.5 Polar covalent 0.5 to 2.0 Ionic greater than 2.0 Electronegativity Table 3.5 – 2.5 = 1.0 Polar covalent

10. 6.2 Covalent Bonding What type of bond is Na – Cl ? Nonpolar covalent less than 0.5 Polar covalent 0.5 to 2.0 Ionic greater than 2.0 Electronegativity Table 3.0 – 0.9 = 2.1 Ionic

11. 6.2 Covalent Bonding Polar and Nonpolar Molecules When a molecule has more than two atoms, two factors will determine whether or not the molecule is polar… ________ of atoms ____________ of the molecule Unequal Sharing of Electrons type shape

12. 6.2 Covalent Bonding In a carbon dioxide (CO 2 ) molecule, the polar bonds ______________ out because the molecule is straight in shape or _________________. So this entire molecule is considered ________________ Kind of like a game of tug-o-war that ___________ is winning Unequal Sharing of Electrons δ +δ - 3.5 2.5 3.5 O = C = O cancel linear nonpolar no one

13. 6.2 Covalent Bonding In a water (H 2 O) molecule, the polar bonds do ________ cancel out because the molecule is___________. Or in other words, one side of the water molecule is still partially ________________ while the other side is still partially _________________ Unequal Sharing of Electrons δ – δ + 2.1 H 2.1 H O 3.5 NOT bent positive negative

14. 6.2 Covalent Bonding Polar molecules, due to their opposite charges, can also attract ________ _______________ and form additional bonds Due to the attraction between polar molecules, water exhibits… ___________ tension a __________ boiling point than other molecules similar to it in size Attraction Between Molecules oneanother surface higher

15. 6.2 Covalent Bonding Surface Tension

16. 6.2 Covalent Bonding The attractions between polar molecules are _______________ than the attractions among nonpolar…but nonpolar attractions do ____________ They explain why CO 2 and N 2, both normally __________, can be stored as solids or liquids at ___________ temperatures and ___________ pressures Attraction Between Molecules stronger exist gases lowerhigher

17. 6.2 Covalent Bonding Assessment Questions 1.What is the difference between a polar and nonpolar molecule? Partial opposite charges Partial charges cancel out

18. 6.2 Covalent Bonding Assessment Questions 2.What determines whether a molecule is polar? a.type of atoms and shape of molecule b.mass of atoms and number of valence electrons c.type and mass of atoms d.ionization energy and number of covalent bonds

19. 6.2 Covalent Bonding Assessment Questions 3.Why does water have a much higher boiling point than methane? a.Methane molecules are more polar, so its molecules have stronger attractive forces. b.Partial charges on the polar water molecules increase attractive forces between molecules. c.A water molecule has much more mass than a methane molecule, so water has a higher boiling point. d.Water has a higher boiling point because its molecules do not contain carbon atoms.