1. Covalent bonds, Polar bonds, and Ionic Bonds Students will identify the various types of bonds and the physical properties associated with them.

2. What is a covalent bond? A bond between two nonmetal atoms where the electrons are shared.

3. Why do atoms form covalent bonds? So they can have the same number of electrons as the nearest noble gas.

4. Electronegativity Turn to page 362

5. What is Electronegativity The ability for an atom to attract electrons to itself in a covalent bond. The higher the Electronegativity, the more powerful pull it has on the electrons.The higher the Electronegativity, the more powerful pull it has on the electrons.

6. Electronegativity Trend What is the trend?.

7. Metals and non-metals do not form covalent bonds Nonmetals pull so much more than metals that when paired together, the electron is transferred to the nonmetal. That is why in NaCl, the sodium has a positive charge. And the chlorine has a negative charge. And the chlorine has a negative charge.

8. Tug of War Atoms try to pull electrons to themselves. Electronegativity is the measure of how strong the pull is.

9. So the strong guy pulls the electron more than the weak guy In this case H is positive and F is negative.

10. The Three Types of Bonds

11. Polar Bond vs. Polar Molecule Do all molecules that have polar bonds become polar molecules? No. Because the molecule may be balanced due to opposing forces.

12. Ionic or Covalent Determine if the combinations are ionic or covalent. Na-O C-N H-F

13. Most Ionic Na-O C-N Put the combinations in order of most ionic to most covalent Solution: Find the Electronegativity difference. Na-O =3.5 -.9 = 2.6, C-N = 3.0 -2.5 =.5 Na-O is the most ionic between these two

14. Bonding Effects Physical Properties For Example, ionic bonds are Crystalline solids They have high melting and boiling points They conduct electricity when melted Many soluble in water but not in non-polar liquids

15. ionic substances dissolve in water because water is polar

16. Covalent Gases, liquids, or solids (made of molecules) Low melting and boiling points Poor electrical conductors in all phases Many soluble in non-polar liquids but not in water Show Video from Weber tube Chemical Cocktail Chemical Cocktail

17. Hydrogen Bonding Hydrogen Bonding is an especially powerful type of polar-covalent bonding. If only happens in bonds with: hydrogen and oxygen Hydrogen and nitrogen And hydrogen and fluorine.

18. Examples CO H2OH2OH2OH2O CH 4 NH 3

20. Watch Video on hydrogen Bonding Watch Video on hydrogen Bonding

21. Guessing Boiling Points Which will have the highest boiling point? CH 4 or CH 3 -OH? Explain: The CH 3 -OH is very polar because it has hydrogen bonding. When a molecule is polar the molecules stick to each other causing the boiling point to be high.

22. The Bigger a molecule is the higher the boiling point is Which will have the highest boiling point? CH 4 or H 3 C-CH 3 Explain: Since ethane is a larger molecule it should have the highest boiling point

23. Life Without Hydrogen Bonding Water wouldn’t boil at +100 o C, it would boil at -120 o C All H 2 O on earth would be gas. No snow. Therefore, no skiing. That wouldn’t hurt Utah’s economy because there would be no Utah

24. Life Without Hydrogen Bonding