1. Bonding

2. Representing Valence Electrons Lewis Dot structures Electron dot structures are diagrams that show the valence electrons as dots Electron dot structures are diagrams that show the valence electrons as dots To find the # valence electrons – look at the Group #! To find the # valence electrons – look at the Group #! Valence electrons are the only ones used in chemical bonds Valence electrons are the only ones used in chemical bonds

3. 3 Important Generalizations about valence electrons 1. Elements in the same group have same number of valence electrons 2. The number of valence electrons is the same as the group number 3. The max number of valence electrons is 8 (exception He)

4. Practice some dot diagrams (Lewis dot diagrams) Li Li Na Na Cl Cl S C N Mg Mg

5. Some common elements

6. So, now why do atoms bond?? Chemical bond: the attractive force that holds 2 atoms together in a more complex unit. Chemical bond: the attractive force that holds 2 atoms together in a more complex unit. Bonds form from the interaction of valence electrons (least tightly bound and most likely to collide!) Bonds form from the interaction of valence electrons (least tightly bound and most likely to collide!) 3 Types of chemical bonds: 1. Ionic Bonds: chemical bond formed through the TRANSFER of 1 or more electrons from on atom to another. They result in the formation of ions! 2.Molecular (Covalent) bonds: chemical bond formed through the sharing of 1 or more pairs of electrons between atoms 3.Metallic Bonds: between 2 metals

7. Ionic Bond Covalent Bond

8. Lewis Dot Diagrams for Ions For cations that drop electrons, no dots needed, just the overall charge For cations that drop electrons, no dots needed, just the overall charge For anions that gain electrons the dots are added along with the overall charge For anions that gain electrons the dots are added along with the overall charge Use brackets!!! Use brackets!!!

9. Octet Rule All atoms want to attain stability with a full valence shell so they attempt to attain a noble gas configuration (8 valence electrons) All atoms want to attain stability with a full valence shell so they attempt to attain a noble gas configuration (8 valence electrons) Having a full octet changes the way an atom behaves Having a full octet changes the way an atom behaves Ex. Na metal reacts violently with water but the Na + ion is very UNreactive. It now behaves like the Noble Neon! Ex. Na metal reacts violently with water but the Na + ion is very UNreactive. It now behaves like the Noble Neon! http://www.youtube.com/watch?v=ODf_sPexS2Q

11. Na and Cl combine in a 1:1 ratio to form NaCl. Why do sodium atoms form Na + and not Na 2+ ? In general, what determines the specific number of electrons lost or gained in the electron transfer process?Na and Cl combine in a 1:1 ratio to form NaCl. Why do sodium atoms form Na + and not Na 2+ ? In general, what determines the specific number of electrons lost or gained in the electron transfer process? The Octet Rule! Atoms tend to gain or lose electrons until they have obtained an electron configuration that is the same as a noble gas!

12. Predicting Sign and Magnitude of Ionic Charge How many electrons must each of the following atoms lose or gain in order to obtain a noble gas electron configuration? How many electrons must each of the following atoms lose or gain in order to obtain a noble gas electron configuration? What is the chemical symbol for the ion produced from the gain/loss? What is the chemical symbol for the ion produced from the gain/loss? A. N B. S C. K D. Mg

13. I. METALLIC BONDING Occurs between: Occurs between: –Atoms of a metal –Example: Cu(s), Ag(s) http://www.mse.cornell.edu/courses/engri111/im ages/metalpic.gif

14. I. METALLIC BONDING Electrons are: Electrons are: –Mobile –Free flowing –AKA “Sea of mobile electrons”

15. I. METALLIC BONDING Properties: Properties: –Good conductors of heat and electricity –High melting point –Malleable Malleable copper ribbon - http://www.onr.com/user/cardan/allie dHealth/surgeTech/images/instra/04 Malleable.jpg http://en.wikipedia.org/wiki/Image:Metallic_bond_Cu.svg

16. Topic 3: METALLIC BONDING The mobile electrons can carry heat and electricity from atom to atom. The mobile electrons can carry heat and electricity from atom to atom. This is why metals are good conductors. This is why metals are good conductors.

17. II. IONIC BONDING Electrons are: Electrons are: –Transferred from one atom to another. http://www.emu.dk/elever7- 10/fag/fys/temaer/kemisk_binding/bindinger/ionbinding/

18. TOPIC: IONIC BONDING Occurs between: Occurs between: –Metal and Non-metal –Forms a lattice structure –Examples: NaCl, MgF 2, CaBr 2 http://academics.vmi.edu/chem_jt/CH131/ionic_covalent_bonding.htm

19. II. IONIC BONDING Properties: Properties: –High melting point –Conduct electricity in solution http://employees.csbsju.edu/HJAKUBOWSKI/classes/ch111/olsg- ch111/chemrxs/animlightnacl.gif

20. In the following example, identify which element loses and electron and which gains… http://www.emu.dk/elever7- 10/fag/fys/temaer/kemisk_binding/bindinger/ionbinding/

21. The electronegativity difference between the two elements must be greater than 1.7 The electronegativity difference between the two elements must be greater than 1.7 Ex: What is the electronegativity difference in LiF? Ex: What is the electronegativity difference in LiF? F = 4.0 Li = 1.0 F = 4.0 Li = 1.0 Difference = 4.0 – 1.0 = 3.0 = IONIC Difference = 4.0 – 1.0 = 3.0 = IONIC II. IONIC BONDING

22. Which atom lost an electron? Which atom gained an electron? What is the net charge on each atom after the electron is transferred? Make an observation about the atomic radius of the metal. Make an observation about the atomic radius of the nonmetal.

23. Use your prior knowledge to determine which two elements are represented in the above diagram. Lithium and Fluorine http://en.wikipedia.org/wiki/Ionic_bond

24. Generalizations about ionic bonding Metals containing 1, 2 or 3 electrons (Groups IA, IIA and IIIA) tend to lose electrons. Group IA lose 1 electron and form a +1 charge, Group IIA lose 2 Electrons and form +2 etc… Metals containing 1, 2 or 3 electrons (Groups IA, IIA and IIIA) tend to lose electrons. Group IA lose 1 electron and form a +1 charge, Group IIA lose 2 Electrons and form +2 etc… Nonmetals containing 5,6,7 electrons (Groups VA, VIA, VIIA) tend to gain electrons. Group VA nonmetals form -3 ions, Group VIA gain 2 electrons forming -2 ions ets… Nonmetals containing 5,6,7 electrons (Groups VA, VIA, VIIA) tend to gain electrons. Group VA nonmetals form -3 ions, Group VIA gain 2 electrons forming -2 ions ets… Group IVA are unique. They can form + 4 or – 4 but most cases form covalent bonds (sharing electrons) Group IVA are unique. They can form + 4 or – 4 but most cases form covalent bonds (sharing electrons) Usually contain a metal and a non metal Usually contain a metal and a non metal

25. Ionic Compounds Are always neutral since the number of electrons lost is the same as the number gained. Are always neutral since the number of electrons lost is the same as the number gained. Ionic charge determines the ionic formula Ionic charge determines the ionic formula Ex. K + and S 2-. K has one electron to give away and S wants to pick up 2 so 2 K have to combine with one S. The resulting formula is K 2 S. Ex. K + and S 2-. K has one electron to give away and S wants to pick up 2 so 2 K have to combine with one S. The resulting formula is K 2 S.

26. Using Lewis Structures to dpict ionic compounds Show the formation of the following ionic compounds using Lewis structures Show the formation of the following ionic compounds using Lewis structures K 3 P K 3 P NaF NaF Na 2 O Na 2 O

27. Chemical Formulas for ionic compounds Since total electron loss always equals total electron gain in the transfer process, ionic compounds are always neutral. NO NET CHARGE Since total electron loss always equals total electron gain in the transfer process, ionic compounds are always neutral. NO NET CHARGE Therefore…the ratio in which positive and negative ions combine is the ration that acheives neutrality for the resulting compound Therefore…the ratio in which positive and negative ions combine is the ration that acheives neutrality for the resulting compound When K + and S 2- combine, K has 1 electron to give away but S needs 2 so the resulting formula will be K When K + and S 2- combine, K has 1 electron to give away but S needs 2 so the resulting formula will be K 2 S

28. Determine the chemical formula for the compound that is formed when each of the ions interact Ba 2+ and Cl - Ba 2+ and Cl - Ba 2+ and S 2- Ba 2+ and S 2- Ba 2+ and N 3- Ba 2+ and N 3-

29. Ionic Bonding http://www.youtube.com/watch?v=QqjcCvzWwww

30. http://www.dlt.ncssm.edu/core/Chapter9- Bonding_and_Geometry/Chapter9- Animations/IonicBonding.html http://www.dlt.ncssm.edu/core/Chapter9- Bonding_and_Geometry/Chapter9- Animations/IonicBonding.html http://www.dlt.ncssm.edu/core/Chapter9- Bonding_and_Geometry/Chapter9- Animations/IonicBonding.html http://www.dlt.ncssm.edu/core/Chapter9- Bonding_and_Geometry/Chapter9- Animations/IonicBonding.html

31. PRACTICE QUESTION Which compound contains a bond with the least ionic character? Which compound contains a bond with the least ionic character? 1)CO 2)CaO 3)K 2 O 4)Li 2 O

32. Let’s practice! Determine the chemical formula for the ionic compound formed when each of the following ions react. Determine the chemical formula for the ionic compound formed when each of the following ions react. 1. Ba 2+ and Cl - 2. Ba 2+ and S 2- 3. Ba 2+ and N 3- 4. Na + and S 2- 5. Mg 2+ and F - 6. Ca 2+ and N 3-

33. Polyatomic IOns An ion formed from a group of atoms held together by covalent bonds An ion formed from a group of atoms held together by covalent bonds Chemical formulas written in the same way as single ions – it is treated as an individual unit Chemical formulas written in the same way as single ions – it is treated as an individual unit See Reference table E See Reference table E

34. Polyatomic ions Compounds made with polyatomic ions contain BOTH covalent AND ionic bonds. Compounds made with polyatomic ions contain BOTH covalent AND ionic bonds. The polyatomic ion is created through covalent bonds. The polyatomic ion is created through covalent bonds. The final compound is made through ionic bonds. The final compound is made through ionic bonds.

35. III. COVALENT/MOLECULAR BONDING Occurs between: –T–T–T–Two or more non-metals –E–E–E–Examples: HHHH2O, CO2, CH4, NH3, O2, Cl2 http://www.yesnet.yk.ca/schools/wes/projects/options_shel_silverstein/animation_poetry_projects/robyn%20/molecule.gif

36. Covalent Bond Forms between 2 non metal atoms Forms between 2 non metal atoms Bond is formed by electron sharing Bond is formed by electron sharing When electrons are shared the orbitals overlap When electrons are shared the orbitals overlap

37. http://www.accs.net/users/kriel/chapter%20seven/water%20polar.gif III. COVALENT/MOLECULAR BONDING Electrons are: Electrons are: –Shared between atoms.

38. III. COVALENT/MOLECULAR BONDING Properties: Properties: –Soft –Poor conductors of heat and electricity –Low boiling point and melting point

39. III. COVALENT/MOLECULAR BONDING There are two types of covalent bonds There are two types of covalent bonds 1.Polar 2.Nonpolar

40. Covalent/Molecular Bonding http://ithacasciencezone.com/chemzone/lessons/03bonding/dogbonds.htm http://ithacasciencezone.com/chemzone/lessons/03bonding/dogbonds.htm

41. III. COVALENT/MOLECULAR BONDING 1. Polar Covalent  Occurs between two different nonmetals  The electronegativity difference is between 0.4 and 1.7  Unequal sharing of electrons  Examples- HCl, HF, CCl 4  Calculate the electronegativity difference in the molecule NH 3. Is it polar?

42. http://www.dlt.ncssm.edu/core/Chapter9- Bonding_and_Geometry/Chapter9- Animations/PolarBonding.html http://www.dlt.ncssm.edu/core/Chapter9- Bonding_and_Geometry/Chapter9- Animations/PolarBonding.html http://www.dlt.ncssm.edu/core/Chapter9- Bonding_and_Geometry/Chapter9- Animations/PolarBonding.html http://www.dlt.ncssm.edu/core/Chapter9- Bonding_and_Geometry/Chapter9- Animations/PolarBonding.html

43. III. COVALENT/MOLECULAR BONDING 2. Nonpolar Covalent  Occurs between two of the same nonmetal.  Equal sharing of electrons  Electronegativity difference is 0.0-0.4  Examples: Diatomic molecules  H 2,O 2, F 2,Br 2,I 2,N 2,Cl 2  Just remember…  HOFBRINCL!!!!

44. Differences between Ionic and Covalent compounds Ionic Compounds Ionic Compounds Crystalline solids (made of ions) Crystalline solids (made of ions) High melting and boiling points High melting and boiling points Conduct electricity when melted Conduct electricity when melted Many soluble in water but not in nonpolar liquid Many soluble in water but not in nonpolar liquid Covalent Compounds Covalent Compounds Gases, liquids, or solids (made of molecules) Gases, liquids, or solids (made of molecules) Low melting and boiling points Low melting and boiling points Poor electrical conductors in all phases Poor electrical conductors in all phases Many soluble in nonpolar liquids but not in water Many soluble in nonpolar liquids but not in water

45. Bonds Summary Sharing Sharing Non Polar – Even Non Polar – Even Polar – Uneven Polar – Uneven Ionic - Transfer Ionic - Transfer EN difference EN difference 0-0.4 Non polar 0-0.4 Non polar 0.4- 1.7 Polar Covalent 0.4- 1.7 Polar Covalent > 1.7 Ionic > 1.7 Ionic

46. Let’s look at the air we breathe…

47. Energy and Bonds Energy and Bonds BARF!!!! BARF!!!! B reaking bonds A bsorbs energy B reaking bonds A bsorbs energy Energy is R eleased when bonds are F ormed Energy is R eleased when bonds are F ormed

51. REVIEW Identify the type of bonding in the following molecules: Identify the type of bonding in the following molecules: –MgF 2 –KCl –I 2 –CO 2 –Br 2 –Ag(s) Ionic Nonpolar Covalent Polar Covalent Nonpolar Covalent Metallic

52. Lewis Structures for covalent compounds Common practice is to represent the shared electrons with a dash The number of covalent bonds that an atom forms is equal to the number of electrons it needs to achieve stable octet. Sharing one pair is a single bond Sharing 2 pairs – double bond Sharing 3 pairs – triple bond The more you share the stronger the bond is!