Lesson 1 Intro to Chemical Bonding
- 1. Lesson 1: Introduction to Chemical Bonding Covalent Bonding Unit
- 2. Targets I can define chemical bond. I can describe covalent bonding. I can classify bonding type according to electronegativity differences.
- 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. 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. 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. IONIC – Metal + nonmetal Periodic Table COVALENT – 2 nonmetals
- 7. Types of Covalent Bonds Nonpolar covalent bond – electrons are shared equally
- 8. Types of Chemical Bonds Polar covalent – electrons are not shared equally because one atom attracts the shared electrons more than the other atom
- 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. 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. Electronegativity Values Increases from left to right across a period Decreases down a group of representative elements
- 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. 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. Covalent Bonding Covalent Bonding and Molecular Compounds
- 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. Formation of a Covalent Bond Nature favors chemical bonding because most atoms have lower potential energy when they are bonded to other atoms.
- 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. 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. 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. 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. 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. 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. Practice What is the relationship between bond energy and bond length?
- 25. Practice What is the relationship between bond energy and bond length? The bond length decreases as the strength of the bond increases.
- 26. Practice Arrange the following in order of increasing bond strength: C–Cl, C–I, H–F, and I–I SKIP
- 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. Practice Problems Which pair of bonded atoms has the strongest bond?
- 29. Practice Problems Which pair of bonded atoms has the strongest bond? H – F
- 30. Practice Problems Which pair of bonded atoms has the weakest bond?
- 31. Practice Problems Which pair of bonded atoms has the weakest bond? I – I
- 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. 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. Practice Problems Determine the number of valence electrons in each of the following atoms. Lithium Sulfur Carbon Neon
- 35. Practice Problems Determine the number of valence electrons in each of the following atoms. Lithium - 1 Sulfur - 6 Carbon -4 Neon - 8