1. CHEMICAL BONDING

3. CRYSTALLINE SOLIDS Sprinkle a few grains of NaCl (salt) on the black piece of paper Use the lens to examine the NaCl closely Write down some observations. What shape is it? What color is it? How big is it? Are all the same shape? …TO BE CONTINUED

4. WHAT ARE CHEMICAL BONDS? STRONG FORCES THAT HOLD ATOMS TOGETHER Molecular formula Ball & stick model Space filling model Structural formula Perspective Condensed structural formula

5. H2OH2O 2 hydrogen atoms 1 oxygen atom CHEMICAL FORMULA Shows 1. elements in the compound 2. ratio of their atoms

6. WHY DO ATOMS FORM BONDS? TO ACHIEVE A STABLE ELECTRON CONFIGURATION ATOMS WITH A FULL VALENCE SHELL ARE VERY STABLE (OCTECT RULE) NOBLE GASES ARE VERY STABLE AND DO NOT REACT ATOMS THAT REACT EASILY ARE UNSTABLE

7. ALKALI METALS ARE VERY REACTIVE

8. HOW DO IONIC BONDS FORM? TRANSFER OF ELECTRONS BETWEEN METALS & NON-METALS 1.NON-METAL STEALS A METAL’S ELECTRON(S) 2.NEGATIVE ION (ANION) IS FORMED FROM THE EXTRA ELECTRON 3.POSITIVE ION (CATION) IS FORMED FROM THE LOSS OF THE ELECTRON 4.CHARGES FORMED ARE CALLED OXIDATION NUMBERS 5.ATTRACTION BETWEEN THE IONS FORMS THE IONIC BOND

9. ION CHARGE or OXIDATION NUMBER The number of electrons gained or lost to become stable

10. HOW DO IONIC BONDS FORM? TRANSFER OF ELECTRONS BETWEEN METALS & NON-METALS

11. CATIONS AND ANIONS

12. THE TRANSFER OF ELECTRONS CREATES IONS

13. IONIC COMPOUNDS STRONG ATTRACIONS BETWEEN PARTICLES FORM CRYSTAL LATTICES CONDUCT ELECTRICITY WHEN DISSOLVED MELT AND BOIL AT HIGH TEMPERATURES

14. WHY DOES AN ION’S ABILITY TO CONDUCT ELECTRICITY MATTER TO ME? Electricity allows your nervous system to send signals to your brain. These signals are actually electrical charges that are delivered from cell to cell, allowing for nearly instantaneous communication

15. IONS CONDUCT ELECTRICITY WHEN DISSOLVED Here's a dead cuttlefish. Soy sauce is being poured on it. Soy sauce is very, very high in sodium. Sodium is responsible for a lot of the activity in nerves, so when you pour lots of it on the dead fish's nerves it flinches and spasms. The dish is called odori-don for those who plan to avoid it forever.

16. NAMING IONIC COMPOUNDS WRITE THE METAL (CATION) FIRST AND THE NON-METAL (ANION) SECOND USE SUBSCRIPTS TO INDICATE THE NUMBER OF EACH TYPE OF ATOM CHANGE THE LAST SYLLABLE OF THE CATION TO “-IDE”

17. MODELING IONIC BONDING NaCl Sodium Chloride

18. CRYSTALLINE SOLIDS ADD SALT INTO WATER AND STIR UNTIL NO MORE SALT WILL DISSOLVE LABEL A DISH AND COVER THE BOTTOM WITH YOUR SALT SOLUTION …TO BE CONTINUED

19. CRYSTALLINE SOLIDS How did the appearance of the salt change between today and last class? Draw a diagram of the crystals you see today and compare them to last class. Would you expect all salt crystals to have the same shape? Why or why not? Use what you know about crystalline solids to explain the shape of the new crystals.

20. WHAT ARE THE MAIN FEATURES OF IONIC BONDS? TRANSFER OF ELECTRONS FORMS IONS ATTRACTION FORMS BOND STRONG, CRYSTALLINE LATTICES FORM

21. COVALENT Together Mutually In common Valence electron: An electron in one of the outer shells of an atom; can form chemical bonds with other atoms

22. WHAT IS A COVALENT BOND? Attraction between two atoms that share an electron; forms a molecule non-metal + non- metal Two hydrogens share their electrons with one oxygen to form water

23. WHY DO COVALENT BONDS FORM? Atoms share electrons to form stable electron configurations Remember 2-8-8: All atoms want a full outer shell

24. HOW DO COVALENT BONDS FORM? Two atoms share two electrons to complete their outer shell One electron comes from each atom Can be single, double, or triple bonds

25. WHAT ARE THE PROPERTIES OF COVALENT MOLECULES? Weak attractions between molecules Lower melting and boiling points Do not conduct electricity

26. ARE ELECTRONS ALWAYS SHARED EQUALLY? NO! Non-polar molecule: equal sharing of electrons Polar molecule: unequal sharing of electrons – molecules attract each other Non-polar Polar

30. HOW CAN YOU TELL WHICH TYPE OF BOND WILL FORM? Electronegativity: ability to attract electrons The type of bond is determined by the difference in electronegativity Electronegativity Difference Type of Bond 0.0-0.4Nonpolar Covalent 0.5-2.0Polar Covalent Greater than 2.0Ionic NaCl 0.9 3.0 3.0 – 0.9 = 2.1

31.  Nonpolar  Polar  Ionic View Bonding Animations.Bonding Animations Covalent vs Ionic Bonding

32. Comparison Chart IONIC COVALENT Electrons Melting Point Soluble in Water Conduct Electricity Other Properties transferred from metal to nonmetal high yes (solution or liquid) yes crystal lattice of ions, crystalline solids shared between nonmetals low no usually not molecules, odorous liquids & gases