Chapter 6: Chemical Bonding Covalent Focus 6.1 Intro to Bonding 6.2 Lewis Structures 6.3 Covalent Formulas

6.1 Intro to Bonding Learning Targets Describe and explain chemical bonding. Describe ionic and covalent bonding.

6.1 Intro to Bonding Chemical Bond: Force of attraction between two atoms Due to mutual attraction of nuclei for electrons

6.1 Intro to Bonding Why do atoms form bonds? Bonds allow atoms to become more stable by achieving lower energy Forming a bond releases energy Breaking a bond absorbs energy Atoms gain or lose electrons to achieve noble gas configuration (full shell)

6.1 Intro to Bonding Octet Rule: Atoms tend to gain, lose, or share electrons to get 8 valence electrons in order to achieve a noble gas configuration Li O Ne C

6.1 Intro to Bonding Electronegativity Measures how strongly an atom pulls electrons towards it

6.1 Intro to Bonding What type of bond? Metals-metals: Metallic Metal-nonmetal: Ionic Nonmetal-nonmetal: Covalent Polar if atoms are different from each other

6.1 Intro to Bonding 1. H –C 2. N—N 3. Cu—Zn 4. Cs—F 5. C—F Classify each of the following bonds: 1. H –C 2. N—N 3. Cu—Zn 4. Cs—F 5. C—F

6.1 Intro to Bonding Ionic Bond Bond formed by attraction between cation and anion One atom loses e-, one gains e-

6.1 Intro to Bonding Properties of Ionic Compounds 1. Crystalline Orderly arranged pattern of cations and anions 2. Solid 3. High Melting/Boiling Points

6.1 Intro to Bonding 4. Hard and Brittle 5. White or Bright colors 6. Dissolve in Water 7. Conduct electricity Break apart into ions in water

6.1 Intro to Bonding Covalent bond: Polar covalent: Two atoms share electrons to gain an octet Polar covalent: Bond formed by two elements that have different electronegativity Electrons spend more time with one atom Slight charges on atoms Dissolve in polar solvents (water, ethanol)

6.1 Intro to Bonding Nonpolar covalent: Bond formed by two elements that have the same or similar electronegativity Electrons spend equal time with each atom No charge on atoms Dissolve in nonpolar solvents (hexane)

6.1 Intro to Bonding Properties of Covalent Compounds 1. Crystalline or Amorphous 2. All phases 3. Soft 4. Low melting/boiling point

6.1 Intro to Bonding 5. Dull Colors 6. Soluble based on polarity Polar dissolve; Nonpolar do not 7. Nonconductors

6.1 Intro to Bonding Metallic Bond Positive nuclei (cations) exist separately in a sea of electrons

6.1 Intro to Bonding Properties of Metals 1. Conduct heat and electricity 2. Malleable 3. Ductility 4. Lustrous

6.2 Lewis Structures Learning Targets: Draw Lewis dot structures for covalent molecules. Determine the polarity of a molecule. Use VSEPR to determine shapes of molecules.

6.2 Lewis Structures Lewis Dot Structures Bonding Pair Lone Pair Representation of molecules using nonbonding e-, bonding e-, and atoms Bonding Pair 2 shared electrons Lone Pair 2 electrons not in a bond

6.2 Lewis Structures 1. Br2 2. N2 3. H2O 4. CH3I

6.2 Lewis Structures 5. HNO 6. C2H6 7. C2H4

6.2 Lewis Structures Polarity Measure of uneven distribution of electrons throughout a molecule 2 things to look for Asymmetry around central atom Different elements Lone pairs

6.2 Lewis Structures Determine if polar or nonpolar 1. Br2 2. NH3 3. C2H6 4. CH3Cl 5. C2H4 6. H2O

6.2 Lewis Structures Octet Exceptions B: BH3 I: IF3 Xe: XeF4

6.2 Lewis Structures Valence Shell Electron Pair Repulsion (VSEPR) theory: Predicts shapes of covalent molecules using valence electrons and bonds Electron pairs repel each other Look at central atom (with most atoms attached) Count atoms attached and lone pairs (only on central atom)

6.3 Covalent Formulas Learning Targets: Write names and formulas of covalent compounds.

6.3 Covalent Formulas Monoatomic Diatomic Made of individual atoms Made of 2 atoms covalently bonded 7 elements always found in pairs when pure element Diatomic 7: H2 , N2 , O2 , F2 , Cl2 , Br2 , I2

6.3 Covalent Formulas Prefixes Prefix Number Mono- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5 Hexa- 6 Hepta- 7 Octa- 8 Nona- 9 Deca- 10

6.3 Covalent Formulas Writing a formula from a name: Only nonmetals 1. In order of name, write symbols 2. Prefixes determine subscript (# of atoms) No prefix on 1st element  1 atom

6.3 Covalent Formulas You try! 1. Dihydrogen monosulfide 2. Carbon tetrahydride 3. Iodine pentafluoride 4. Hydrogen monochloride 5. Triphosphorous pentoxide

6.3 Covalent Formulas Naming a covalent compound Only nonmetals 1. In order of formula, write name of each element. 2. Add prefixes in front to show amount If only 1 of first element, ignore “mono” 3. Change endings (all but first) to –”ide”

6.3 Covalent Formulas You try! 1. CO2 2. SeO 3. IF7 4. PH3 5. N2O5