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Chemical Bonding

Chemical Bonding. It’s all about togetherness…. Bonding .1 Can you…. Define chemical bond? Explain why most atoms form bonds? Describe ionic and covalent bonding? Explain why most chemical bonds are neither purely ionic or purely covalent?

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Chemical Bonding

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  1. Chemical Bonding It’s all about togetherness….

  2. Bonding .1 Can you… • Define chemical bond? • Explain why most atoms form bonds? • Describe ionic and covalent bonding? • Explain why most chemical bonds are neither purely ionic or purely covalent? • Classify bonds as either ionic, covalent or polar according to the differences in electronegativity?

  3. What is a chemical bond? • A mutual attraction between the nuclei and valence electrons of different atoms.

  4. Main Types of Bonds • Ionic- electrons are exchanged • Occurs between ions • Very strong bond, with one major weakness: breakable with water • Covalent- electrons are shared • May be polar or non-polar • Do not break with addition of water • Metallic- electrons are in a “sea” around nuclei • Allows for malleability and ductility of metals

  5. Table of ElectronegativitiesYou can print one of these from the Homework page

  6. How do I know what type of bond is formed between two atoms? • Type of bond is determined by the difference of electronegativities of the atoms.

  7. What type of bond? • Use page 194 to reference electronegativities • HF • |4.0-2.1| = 1.9 • Ionic bond

  8. What type of bond? • Use page 194 or table to reference electronegativities • CH4 • |2.5-2.1| = 0.4 • polar covalent (slightly polar)

  9. What type of bond? • Use page 194 to reference electronegativities • H2O • |2.1-3.5| = 1.4 • polar covalent (highly polar)

  10. What type of bond? • Use page 194 to reference electronegativities • H2 • |2.1-2.1| = 0 • covalent (purely covalent)

  11. What type of bond? • Use page 161 to reference electronegativities • NaCl • |0.9-3.0| = 2.1 • ionic

  12. Can you… • Define chemical bond? • Explain why most atoms form bonds? • Describe ionic and covalent bonding? • Explain why most chemical bonds are neither purely ionic or purely covalent? • Classify bonds as either ionic, covalent or polar according to the differences in electronegativity?

  13. ½ sheet CFU 3 points SCl2 • What is the electronegativity difference? • What type of bond? • What is your justification? |2.5 - 3.0| = 0.5 Polar Covalent Electronegativity difference between .3 and 1.7.

  14. Homework … • Packet page 8 • Venn diagram • Compounds HandOut

  15. ½ sheet quiz Honors • Draw the Lewis structure for HCO2H • Remember to count the valence e-

  16. Covalent bonding and molecular compounds

  17. Objectives…. Can you… • Define molecule and molecular formula? • Explain the relationships among potential energy, bond length, and bond energy? • Create Lewis diagrams for each element and simple molecules? • State the octet rule?

  18. Basic Vocabulary • Molecule: neutral group of atoms held together by covalent bonds • Chemical (molecular) formula: indicates the relative numbers of each type of atom using symbols and subscripts found in a single molecule of the compound

  19. Bonding Forces

  20. Forming a Covalent Bond • Bonding occurs when the potential energy is at its minimum • Bond length is a function of the attractive and repulsive forces

  21. The Octet Rule • Chemical compounds form so that each atom has a complete valence shell of electrons, either by sharing, gaining, or losing electrons (most ns2np6)

  22. Electron Dot Diagrams • Show only the valence electrons of an atom or ion 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p2

  23. Bohr Diagrams

  24. Electron Dot Diagrams • Show only the valence electrons of an atom or ion

  25. Class work • Open your packet to page 9 and work on the LEWIS Dot Worksheet. • You may work with Electron Dot Notation Partner. (10 minutes)

  26. Lewis Dot Diagrams • Demonstrate shared and unshared electron pairs in compounds H H:O: : :

  27. Rules for Creating Lewis Dot Diagrams • Determine the number of each type of atom in the compound • Write the electron-dot notation for each type of atom • Determine the total number of valence electrons available

  28. Rules for Creating Lewis Dot Diagrams • Arrange atoms to form a skeleton structure and connect adjacent atoms with paired electrons • Add unshared pairs of electrons around each non-metal (not H) until octet is reached • Count the number of electrons and compare to step 3 • If incorrect, try creating double and triple bonds.

  29. Create the Lewis-Dot for Methane (CH4) Determine the number of each type of atom in the compound carbon-1; hydrogen-4 Write the electron-dot notation for each type of atom C H . . . . .

  30. Rules for Creating Lewis Dot Diagrams Determine the total number of valence electrons available • Carbon -4 valence electrons • Hydrogen -1 valence electron (x4)=4 e- • Total=4+4=8

  31. Rules for Creating Lewis Dot Diagrams • Arrange atoms to form a skeleton structure and • connect adjacent atoms with paired electrons H . . . . H C H . . . . H

  32. Rules for Creating Lewis Dot Diagrams • Add unshared pairs of electrons around each non-metal (not H) until octet is reached H . . . . H C H . . . . H

  33. Rules for Creating Lewis Dot Diagrams • Count the number of electrons and compare to step 3 • If incorrect, try creating double and triple bonds. H . . . . H C H . . . . H

  34. Rules for Creating Lewis Dot Diagrams • NH3 • Nitrogen- 1; hydrogen- 3 • Valence electrons = 5+3(1)=8 . . H . N . . .

  35. Rules for Creating Lewis Dot Diagrams . . . . . . . . H N H H

  36. Rules for Creating Lewis Dot Diagrams • CO2

  37. Can you… • Define molecule and molecular formula? • Explain the relationships among potential energy, bond length, and bond energy? • Create Lewis diagrams for each element and simple molecules? • State the octet rule?

  38. Homework • Packet pg 9 and 10 • Chemical Nomenclature and Formula Writing

  39. Formula Quiz 2A • RbAt • (H3O)2Se • Cd3N2 • Fe(NO2)3 • CaI2 • Mercury (II) Astatide • Cesium phosphite • Barium chlorite • Francium permanganate • Beryllium phosphide

  40. ½ sheet quiz • Draw Lewis Dot Structures for each… • Al • CH4 • NF3 . . . C Al . . . H . . . . . . . . . . . H H . . . H . . . . . . . . . F N F . . . . . . . . F

  41. Ionic bonding and ionic compounds

  42. Types of Chemical Formulas Molecular Formula Formula Unit Used for ionic compounds Gives the ratio of anions and cations, but not the exact number • Used for molecules • Gives exact numbers of each type of atom

  43. Lattice Energy • Energy released when 1 mole of an ionic crystal compound is formed from gaseous ions.

  44. Polyatomic ions • A charged group of covalently bonded atoms • Act as a single unit • Lewis structures are the same as for any covalently bonded compound

  45. Can you… • Compare and contrast a chemical formula for a molecular compound with one for an ionic compound? • Discuss the arrangement of ions within crystals? • List the distinctive properties of ionic and molecular compounds? • Write the Lewis structure for a polyatomic ion?

  46. Formula Quiz 3B • Cd3N2 • CaI2 • (H3O)2Se • Fe(NO2)3 • RbAt • Barium chlorite • Beryllium phosphide • Cesium phosphite • Francium permanganate • Mercury (II) Astatide

  47. Metallic Bonding

  48. Can you… • Describe the electron sea model of metallic bonding and use it to explain why metals are good conductors of electricity? • Explain why metal surfaces are shiny? • Explain why metals are malleable and ductile while ionic compounds are not?

  49. Metallic Bond • Chemical bond that results from the attraction between metal atoms and the surrounding sea of electrons.

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