Lesson 1 Intro to Chemical Bonding

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Covalent Bonding Unit
Lesson 1 Intro to Bonding

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Lesson 1 Intro to Chemical Bonding

  1. 1. Lesson 1: Introduction to Chemical Bonding Covalent Bonding Unit
  2. 2. TargetsI can define chemical bond.I can describe covalent bonding.I can classify bonding type according to electronegativity differences.
  3. 3. DefinitionsChemical Bond – mutual electrical attraction between the nuclei and valence electrons of different atoms that bind the atoms togetherValence electrons – outermost electrons that are available to be lost, gained, or shared to form a chemical bond
  4. 4. Chemical Bond A force that holds groups of 2 or more atoms together and makes them function as a unit Atom – smallest unit of an element Molecule – Group of covalently bonded atoms Atoms Molecule
  5. 5. Types of Chemical BondsIonic Bonding – (covered in next chapter) a type of bond in which a metal and a nonmetal transfer electronsCovalent Bonding – type of bond in which 2 or more nonmetal atoms share electrons
  6. 6. IONIC – Metal + nonmetalPeriodic Table COVALENT – 2 nonmetals
  7. 7. Types of Covalent BondsNonpolar covalent bond – electrons are shared equally
  8. 8. Types of Chemical BondsPolar covalent – electrons are not shared equally because one atom attracts the shared electrons more than the other atom
  9. 9. Bond TypesVideo
  10. 10. ElectronegativityElectronegativity - measure of an atom’s ability to attract electrons.Electronegativities tend to increase across a period and decrease down a group
  11. 11. Classifying Chemical BondsThe polarity of a bond depends on the difference between the electronegativity values of the atoms forming the bonds.Nonpolar covalent – 0 to 0.3Polar covalent – 0.4 to 1.7Ionic – greater than 1.8
  12. 12. Electronegativity ValuesIncreases from left to right across a periodDecreases down a group of representative elements
  13. 13. PracticeUse electronegativity values to classify the following bonds: a. Sulfur and Hydrogen b. Lithium and Fluorine c. Potassium and Chlorine d. Iodine and Bromine e. Carbon and Hydrogen
  14. 14. PracticeUse electronegativity values to classify the following bonds: a. Sulfur and Hydrogen 2.5 – 2.1 = 0.4; polar covalent b. Lithium and Fluorine 4.0 – 1.0 = 3.0; Ionic c. Potassium and Chlorine 3.0 – 0.8 = 2.2; Ionic d. Iodine and Bromine 2.8 – 2.5 = 0.3; Nonpolar covalent e. Carbon and Hydrogen 2.5 – 2.1 = 0.4 ; polar covalent
  15. 15. Covalent BondingCovalent Bonding and Molecular Compounds
  16. 16. TargetsI can explain why most atoms form chemical bonds.I can explain the relationships among potential energy, distance between approaching atoms, bond length and bond energy.I can state the octet rule.I can determine the number of valence electrons for a given atom.
  17. 17. Formation of a Covalent BondNature favors chemical bonding because most atoms have lower potential energy when they are bonded to other atoms.
  18. 18. Formation of a Covalent BondEach atom has a positive nucleus in the center and negative electrons surrounding the nucleus in a spherical pattern.The positively charged nuclei are attracted to the negatively charged electrons.
  19. 19. Formation of a Covalent BondAs the atoms approach each other, the charged particles interact: nucleus on one atom attracts electrons on the other atom.
  20. 20. Formation of a Covalent BondAs the atoms approach one another, the potential energy decreases.A bond forms when the potential energy is at a minimum.
  21. 21. Formation of a Covalent BondIf the atoms continue to approach one another once the bond forms, the nuclei will begin to repel one another and the potential energy will start to increase.
  22. 22. Characteristics of the Covalent Bond Bond length – distance between two bonded atoms at their minimum potential energy or the average distance between two bonded atoms Bond energy – energy required to break a chemical bond and form neutral isolated atoms - kilojoules per mole (kJ/mol) Bond lengths and bond energies vary with the types of atoms that have combined
  23. 23. The Octet RuleThe octet rule states that atoms tend to lose, gain or share electrons until they are surrounded by 8 electrons in their valence shell.The number of valence electrons is equal to the group number. (Groups 13-18; Group # -10)LABEL YOUR PERIODIC TABLE 1A 8A 2A 3A 4A 5A 6A 7A
  24. 24. PracticeWhat is the relationship between bond energy and bond length?
  25. 25. PracticeWhat is the relationship between bond energy and bond length? The bond length decreases as the strength of the bond increases.
  26. 26. PracticeArrange the following in order of increasing bond strength: C–Cl, C–I, H–F, and I–ISKIP
  27. 27. PracticeArrange the following in order of increasing bond strength: C–Cl, C–I, H–F, and I–I I-I, C-I, C-Cl, H-F
  28. 28. Practice ProblemsWhich pair of bonded atoms has the strongest bond?
  29. 29. Practice ProblemsWhich pair of bonded atoms has the strongest bond? H – F
  30. 30. Practice ProblemsWhich pair of bonded atoms has the weakest bond?
  31. 31. Practice ProblemsWhich pair of bonded atoms has the weakest bond? I – I
  32. 32. Practice ProblemsArrange the following bond lengths in order of increasing bond strength: 72 pm, 149 pm, 53 pm, and 398 pm SKIP
  33. 33. Practice ProblemsArrange the following bond lengths in order of increasing bond strength: 72 pm, 149 pm, 53 pm, and 398 pm 398 pm, 149 pm, 72 pm, 53 pm
  34. 34. Practice ProblemsDetermine the number of valence electrons in each of the following atoms. Lithium Sulfur Carbon Neon
  35. 35. Practice ProblemsDetermine the number of valence electrons in each of the following atoms. Lithium - 1 Sulfur - 6 Carbon -4 Neon - 8

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