Presentation on theme: "Academic Chemistry Mrs. Teates Newport High School"— Presentation transcript:
1Academic Chemistry Mrs. Teates Newport High School Chapter 6 – Chemical BondingAcademic Chemistry Mrs. Teates Newport High School
2Lesson 1 – Introduction to Chemical Bonding Lesson Essential Questions:Why do atoms form chemical bonds?How is the type of chemical bond determined?Vocabulary: chemical bond, ionic bonding, covalent bonding, nonpolar-covalent bonding, polar, polar-covalent bonding
3Vocabulary Chemical Bond attractive force between atoms or ions that binds them together as a unitbonds form in order to…decrease potential energy (PE)increase stability
4Na+ NO3- Vocabulary ION 1 atom 2 or more atoms Monatomic Ion PolyatomicIonNa+NO3-
5Types of Bonds IONIC COVALENT Bond Formatione- are transferred from metal to nonmetale- are shared between two nonmetalsType of Structurecrystal latticetrue moleculesPhysicalStatesolidSolid, liquid, or gasMeltingPointhighlowSolubility inWateryesusually notElectrical Conductivityyes (solution or liquid)noOtherPropertiesodorous
6Types of Bonds METALLIC e- are delocalized among metal atoms Bond Formatione- are delocalized among metal atomsType of Structure“electron sea”PhysicalStatesolidMeltingPointvery highSolubility inWaternoyes (any form)Electrical ConductivityOtherPropertiesmalleable, ductile, lustrous
17More Bond Polarity Practice What type of bonding would be expected between the following atoms?Li and ClCa and GaI and ClK and Na
18Lesson 2 – Covalent Bonding and Molecular Compounds Lesson Essential Questions:How is a molecular compound formed?What are some of the characteristics of a covalent bond?Vocabulary: molecule, chemical formula, molecular formula, bond energy, electron-dot, Lewis structure, structural formula, single bond, multiple bonds, resonance
19VocabularyCovalent bond – bond that is created by the sharing of electronsMolecule – neutral group of atoms held together by covalent bondsMolecular compound – chemical compound made of molecules
20NaCl CO2 Vocabulary CHEMICAL FORMULA IONIC COVALENT Formula Unit MolecularFormulaNaClCO2
21Energy of Bond Formation Potential Energybased on position of an objectlow PE = high stability
22Energy of Bond Formation Potential Energy Diagramattraction vs. repulsionno interactionincreased attraction
23Energy of Bond Formation Potential Energy Diagramattraction vs. repulsionincreased repulsionbalanced attraction & repulsion
24Energy of Bond Formation Bond EnergyEnergy required to break a bondBond EnergyBond Length
25Energy of Bond Formation Bond EnergyShort bond = high bond energy
26Lewis Structures Electron Dot Diagrams Pick the central atom Count the valence electrons (they are what electron dot diagrams show)Place electrons around the atom
27Ne Lewis Structures Octet Rule Most atoms form bonds in order to obtain 8 valence e-Full energy level stability ~ Noble GasesNe
29Practice Drawing Lewis Structures On page 186 in your text book do practice problems #1-4Draw the Lewis structure of ammonia, NH3Draw the Lewis structure for hydrogen sulfide, H2SDraw the Lewis structure for silane, SiH4Draw the Lewis structure for phosphorus trifluoride, PF3
30Multiple Covalent Bonds Some elements can share more than one electron pair.Double bond (two pairs of electrons are shared)Triple bond (three pairs of electrons are shared)
31Practice of Lewis Structures for multiple bonds Draw Lewis structures for each of the following molecules:O2CO2N3N2
32ResonanceOccurs when more than one valid Lewis structure can be written for a particular molecule (due to position of double bond)These are resonance structures of benzene.The actual structure is an average (or hybrid) of these structures.
33Resonance in Ozone Note the different location of the double bond Neither structure is correct, it is actually a hybrid of the two. To show it, draw all varieties possible, and join them with a double-headed arrow.
34Polyatomic ions – note the different positions of the double bond. Resonance in a carbonate ion (CO32-):Resonance in an acetate ion (C2H3O21-):
35Molecular Nomenclature Prefix System (binary compounds)1. Less e-neg atom comes first.2. Add prefixes to indicate # of atoms. Omit mono- prefix on first element.3. Change the ending of the second element to -ide.
39Lesson 3 – Ionic Bonding and Ionic Compounds Lesson Essential Questions:How is an ionic bond formed?What are some of the characteristics of an ionic bond?Vocabulary: ionic compound, formula unit, lattice energy, polyatomic ion
40Vocabulary:Ionic compound – composed of positive and negative ions that are combined so that the charges are equal.
41NaCl CO2 Vocabulary CHEMICAL FORMULA IONIC COVALENT Formula Unit MolecularFormulaNaClCO2
42Forming Ionic Compounds Electron dot notation is used to note changes.Form to create an atmosphere of stability
43Lewis Structures and Ionic Compounds Covalent – show sharing of e-Ionic – show transfer of e-
44Characteristics of Ionic Bonding Ions minimize potential energy in crystals by forming a crystal lattice.Distance between all ions represent a balance of attraction between oppositely charged particles and repulsion between like charged particles
45Energy of Bond Formation Lattice EnergyEnergy released when one mole of an ionic crystalline compound is formed from gaseous ions
46Ionic vs. Covalent Ionic High melting temperature High boiling point HardBrittle, because slight shift of crystal can cause it to breakConduct electricity when dissolved in waterCovalentLow melting temperatureLow boiling pointDo not conduct electricityNot as brittle
47Ionic Nomenclature Ionic Formulas Write each ion, cation first. Don’t show charges in the final formula.Overall charge must equal zero.If charges cancel, just write symbols.If not, use subscripts to balance charges.Use parentheses to show more than one polyatomic ion.Stock System - Roman numerals indicate the ion’s charge.
48Ionic Nomenclature Ionic Names Write the names of both ions, cation first.Change ending of monatomic ions to -ide.Polyatomic ions have special names.Stock System - Use Roman numerals to show the ion’s charge if more than one is possible. Overall charge must equal zero.
49Ionic Nomenclature Consider the following: Does it contain a polyatomic ion?-ide, 2 elements no-ate, -ite, 3+ elements yesDoes it contain a Roman numeral?Check the table for metals not in Groups 1 or 2.No prefixes!
50Ionic NomenclatureCommon Ion Charges1+2+3+NA3-2-1-
53Lesson 4 – Metallic Bonding Lesson Essential Questions:How is a metallic bond formed?What are some of the characteristics of a metallic bond?Vocabulary: metallic bond, alloy
54Characteristics of Metallic Bonds Metal ions held together by attraction to free floating electrons. (Sea of electrons)Good conductors of electricity – Why?
55Characteristics of Metallic Bonds Cont. MalleableDuctileBond strength – related to enthalpy of vaporizationThe more energy required to vaporize, the stronger the bond.See table on page 196.
56AlloysA mixture of two or more substances, one of which must be a metal.Common alloys include steel, 14K gold, 18K gold, cast iron, sterling silver, and bronze.Within different alloys, there can be different types of mixtures – ex. SteelWhere do we find alloys?
57Compare/ConstrastUse the 3 circle Venn diagram to compare and contrast ionic, metallic, and covalent bonding.
58Lesson 5 – Molecular Geometry Lesson Essential Questions:How is the VSEPR Theory useful?What are the different forces present in bonding?Vocabulary:VSEPR theory, hybridization, dipole, hydrogen bonding, London dispersion forces
59VSEPR Theory Valence Shell Electron Pair Repulsion Theory Electron pairs orient themselves in order to minimize repulsive forces.
60Lone pairs repel more strongly than bonding pairs!!! VSEPR TheoryTypes of e- PairsBonding pairs - form bondsLone pairs - nonbonding e-Lone pairs repel more strongly than bonding pairs!!!
61VSEPR Theory Lone pairs reduce the bond angle between atoms.
62Determining Molecular Shape Draw the Lewis Diagram.Tally up e- pairs on central atom.double/triple bonds = ONE pairShape is determined by the # of bonding pairs and lone pairs.Know the 8 common shapes & their bond angles!
74Practice ProblemsIdentify the molecular geometry for the following molecules:HICBr4CH2Cl2
75Intermolecular Forces Intermolecular forces = forces between molecules.The boiling point of a liquid is a good measure of the intermolecular forces between its molecules: the higher the boiling point, the stronger the forces between the molecules.Types of intermolecular forcesDipole-dipole forcesHydrogen bondingLondon dispersion forces
76Dipole – Dipole ForcesDipole – created by equal but opposite charges that are separated by a short distance.A dipole is represented by an arrow with its head pointing toward the negative pole and a crossed tail at the positive pole. The dipole created by a hydrogen chloride molecule is indicated as follows:Dipole-dipole forces are the forces of attraction between polar molecules.
77Dipole-dipole forces cont. The negative region in one polar molecule attracts the positive region in adjacent molecules. So the molecules all attract each other from opposite sides.Dipole-dipole forces act at short range, only between nearby molecules.
78Hydrogen BondingHydrogen bonding = intermolecular force in which a hydrogen atom that is bonded to a highly electronegative atom is attracted to an unshared pair of electrons in a nearby molecule.
79London Dispersion Forces London Dispersion Forces = intermolecular attractions resulting from the constant motion of electrons and the creation of instantaneous dipoles.
80Works Cited Modern Chemistry Textbook www.nclark.net