1. Chemical Bonding

2. Chemical Bond: attractive force between atoms or ions that binds them together as a unit atoms form bonds in order to… decrease potential energy (PE) increase stability

3. Covalent bonding — electrons are shared between atoms in a molecule or in polyatomic ions Ionic bonding — positively and negatively charged ions are held together by electrostatic forces electrons are transferred

4. Polar Covalent: An unequal attraction for shared electrons creating partially charged poles- asymmetrical electron density Non-polar: electrons are shared equally- symmetrical electron density δ - symbol for partially negative δ + symbol for partially positive Two Types of Covalent Bonds

6. For Polar Covalent Bonds: higher electronegative atom =  - lower electronegative atom =  + Recall: Electronegativity is the measure of an atom’s ability to attract electrons! Determining Type of Bond Using Electronegativity Difference

7. For Ionic Bonds: The higher electronegative atom forms an anion. (gains electrons) The lower electronegative atom forms a cation. (loses electrons)

8. Determining Type of Bond Using Electronegativity Difference

9. Electronegativity Trend Increases up and to the right.

10. Ionic Polar-covalent Nonpolar-covalent 3.3 1.7 0.3 0 Difference in electronegativities The difference in electronegativity (END) determines bond type.

11. 3.0 - 3.0 = 0.0 Nonpolar 3.0 - 2.1 = 0.9 Polar 3.0 - 0.9 = 2.1 Ionic Polar-covalent Nonpolar-covalent 3.3 1.7 0.3 0 Difference in electronegativities Examples: Cl 2 HCl NaCl

12. Use electronegativity values to classify bonding between: Sulfur (S) and Hydrogen (H) Cesium (Cs) and Fluorine (F) Chlorine (Cl) and Phosphorus (P) Practice

13. Bonding ENDBond type More negative atom S and H2.5 – 2.1 = 0.4polar-covalentsulfur Cs and F4.0 – 0.8 = 3.2ionicfluorine Cl and P3.0 – 2.2 = 0.8polar-covalentchlorine O and O3.5 – 3.5 = 0.0nonpolar-covalentNA Practice Solution

14. 2s 2p2p 1s 2s 1s LiF + - How Does Bonding Work? Ionic Bond is then formed between F - & Li + e - transfer

15. 2s 1s F How Does Bonding Work? Nonpolar Covalent Bond is then formed- F 2 shared e - (overlapping p orbital) 2p2p2p2p 1s 2s F

16. 1s O How Does Bonding Work? Polar Covalent Bond is then formed. Oxygen is more electronegative than hydrogen- creating a polar molecule H 2 O. shared e - (overlapping s & p orbitals) 2p2p 1s H H δ-δ- δ+δ+ δ+δ+

17. Wrapping it Up! Nonpolar Covalent Bond electrons are shared equally symmetrical electron density usually identical atoms

18. Polar Covalent Bond electrons are shared unequally asymmetrical electron density results in partial charges Wrapping it Up!

19. Ionic Bond electrons are transferred ions are formed electrostatic attraction between cations and anions

20. Nonpolar Polar Ionic

21. Ionic – transfer of electrons (Metal + Non-metal) Did you notice this? More Wrapping it Up! Covalent – sharing of electrons (Non-metal + Non-metal) Did you notice this? Non-polar Polar

22. Why do atoms form bonds? EXIT TICKET: