Chemical Bonding

1. Chemical Bonding Chapter 13 Material on Midterm

2. From Glue to Goop • Different types of bonds create differences in the properties of substances

3. Section 1: Electrons and Chemical Bonding • Objectives: • Describe what chemical bonds are • Identify how many valence electrons are in any atom • Explain how you know if an atom is likely to form bonds

4. Section 1: Electrons and Chemical Bonding • Combining Atoms through Chemical Bonding • Most atoms hate being alone…so they bond! • Chemical bonding is the combining of atoms to form molecules or ionic compounds • Properties of new substance are different that the properties of the old substance • The chemical bond is the interaction that holds the two atoms together.

5. 6 + 6 + 12 = C6H12O6 aka glucose

6. Section 1: Electrons and Chemical Bonding • Combining Atoms Through Chemical Bonding • It’s all about the electrons • When bonds form, electrons can… • …be shared • …be gained • …be lost

7. Section 1: Electrons and Chemical Bonding • Electron Number and Organization • We need to organize the electrons so we know what they will do if bonds are formed • Review: How do I know how many electrons at atom has? • Same as its atomic number (proton #)

9. Section 1: Electrons and Chemical Bonding • What are the rules for where the electrons go?

10. Section 1: Electrons and Chemical Bonding • What are the rules for where electrons can go? • Electrons do NOT like each other! • Will try to move FAR away from other electrons • ONLY pair up after 4 are on 2nd level • NSEW

11. Section 1: Electrons and Chemical Bonding • Outer-Level Electrons and Bonding • Only the valence electrons are involved in forming chemical bonds • The valence electrons are the electrons found in the outermost shell of an atom

12. Section 1: Electrons and Chemical Bonding

13. Section 1: Electrons and Chemical Bonding • Valence Electrons and the Periodic Table • Elements in the same group have the same number of valence electrons (generally) • If Lithium has 1…then Sodium, Potassium, rubidium, Cesium, and Francium all have…1!

15. Section 1: Electrons and Chemical Bonding • To Bond or Not to Bond • Not all atoms bond the same • Group 18 have their outmost shell filled. • WANNA GET TO 8! • Group 18 already has 8 (except He), so they’re happy and DO NOT REACT

16. Section 1: Electrons and Chemical Bonding • To Bond or Not to Bond • Filling the Outermost Level • Less than 8? More likely to react. • Will share, take, or lose electron(s) to get to the magic number • What about 2? • Some elements that are small (H, He, Li, Be), will try to get to 2 electrons for that first shell • Will share, take, or lose electron(s) to get to this number

17. Section 1: Electrons and Chemical Bonding • Section Review • Please answer the objectives on your objective summary sheet • Describe what chemical bonds are • Identify how many valence electrons are in any atom • Explain how you know if an atom is likely to form bonds

18. Section 2: Ionic Bonds • Objectives: • Explain how ionic bonds form • Describe how positive and negative ions form • Explain why ionic compounds are neutral

19. Section 2: Ionic Bonds All you need to knowabout ionic bondingis right here

20. Section 2: Ionic Bonds • Forming Ionic Bonds • An ionic bond is a bond that form when electrons are transferred from one atom to another atom • This creates ions, which are charged particles that form when atoms gain or lose electrons • As a result of an ionic bond, either positive or negative ions can form

22. Section 2: Ionic Bonds • Forming Positive ions • Positive ions form when metal atoms lost electrons • Na loses one electron---Na+ • Ca loses two electrons –Ca2+ • By losing electrons, metals can get to the magic number! • Usually 8, could be 2

24. Section 2: Ionic Bonds • Forming Negative Ions • Negative ions form when nonmetal atoms gain electrons • Cl gains one electron – Cl- • O gains two electrons – O2- • By gaining electrons, nonmetals can get to the magic number! • Usually 8, could be 2

26. Section 2: Ionic Bonds • Ionic Compounds • When ionic bonds form, the number of electrons lost by the metal EQUALS the number of electrons gained by the nonmetals • Everyone is happy! • The overall compound is neutral because the ions cancel out

27. Section 2: Ionic Bonds • When ions bond, they form a repeating 3D pattern called a crystal lattice • Strong bonds mean: • High melting points • Brittleness • High boiling points

28. Section 2: Ionic Bonds • Section Review • Please answer the objectives on your objective summary sheet • Explain how ionic bonds form • Describe how positive ions form • Describe how negative ions form • Explain why ionic compounds are neutral

29. Section 3: Covalent and Metallic Bonds • Objectives: • Explain how covalent bonds form • Describe molecules • Explain how metallic bonds form • Describe the properties of metals

30. Section 3: Covalent and Metallic Bonds • What are Covalent Bonds • A covalent bond forms when atoms share one or more pairs of electrons • Occurs between nonmetals • Helps them get to their MAGIC NUMBER (8 or 2)

31. Section 3: Covalent and Metallic Bonds • Covalent Bonds and Molecules • A molecule is the smallest unit of a substance that keeps all the physical and chemical properties of that substance • 2 or more atoms joined in a definite ratio

32. Section 3: Covalent and Metallic Bonds • Covalent Bonds and Molecules • Easier way to draw them– Electron-Dot Diagrams • Remember, only the valence electrons are important for bonding!

33. Section 3: Covalent and Metallic Bonds • Covalent Bonds and Molecules • To make an electron-dot diagram: • Write the symbol of the element in the center • Figure out how many valence electrons it has • Add valence electrons NSEW order • You’re finished!

34. Section 3: Covalent and Metallic Bonds • Examples of electron-dot diagrams

35. Section 3: Covalent and Metallic Bonds • Atom v. molecule

36. Section 3: Covalent and Metallic Bonds

37. Section 3: Covalent and Metallic Bonds • The Simplest Molecules • Must have at least two covalently bonded atoms • 2 of the same element? Diatomic molecules • Remember: HONClBrIF Hydrogen Oxygen Nitrogen Chlorine Bromine Iodine Fluorine

38. Section 3: Covalent and Metallic Bonds • More Complex Molecules • Many different elements • Many based on carbon

39. Section 3: Covalent and Metallic Bonds • Metallic Bonds • Metals have properties like malleability and ductility because of their special bonds • Metallic bonds are bonds from between the attraction of positively charged metal ions and the electrons around them

40. Section 3: Covalent and Metallic Bonds • Movement of Electrons Throughout a Metal • Bonding in metals is a result of the metal atoms being so close to another that their outermost energy levels overlap • Metals surrounded in a “sea” of electrons

41. Section 3: Covalent and Metallic Bonds • Properties of Metals • Conducting Electric Current • Valence electrons that are moving • Reshaping Metals • Electrons free to move around…makes it easy to shape • Ductility • Malleability • Bending without breaking • Electrons can move in response to pressure so they can bend without breaking

42. Section 3: Covalent and Metallic Bonds • Section Review • Please answer the objectives on your objective summary sheet • Explain how covalent bonds form • Describe molecules • Explain how metallic bonds form • Describe the properties of metals