Chemical Bonding I. Introduction to Bonding

2.4.1 Define chemical bond Explain why most atoms form chemical bonds Describe ionic and covalent bonding Classify bonding type according to electronegativity differences Define molecule and molecular formula.OBJECTIVES

Review zWe can also predict what ions an element will form / multiple cations

Vocabulary zChemical Bond yelectrical attraction between nuclei and valence e - of neighboring atoms that binds the atoms together ybonds form in order to… xincrease stability

Vocabulary Octet Rule: Atoms will transfer or share electrons in order to have 8 electrons in their highest energy level. This makes it like a noble gas

Vocabulary CHEMICAL FORMULA Molecular Formula Unit IONICCOVALENT CO 2 NaCl

Vocabulary COMPOUND Ternary Compound Binary Compound 2 elements more than 2 elements NaNO 3 NaCl

Vocabulary ION Polyatomic Ion Monatomic Ion 1 atom 2 or more atoms NO 3 - Na +

IONIC COVALENT Bond Formation Type of Structure Solubility in Water Electrical Conductivity Other Properties e - are transferred from metal to nonmetal high yes (solution or liquid) yes e - are shared between two nonmetals low no usually not Melting Point crystal lattice true molecules Types of Bonds Physical State solid liquid or gas

“electron sea” METALLIC Bond Formation Type of Structure Solubility in Water Electrical Conductivity Other Properties Melting Point Types of Bonds Physical State e - are delocalized among metal atoms very high yes (any form) no malleable, ductile, lustrous solid

RETURN Types of Bonds

RETURN Types of Bonds

Ionic Bonding - Crystal Lattice RETURN Types of Bonds

Covalent Bonding - True Molecules RETURN Types of Bonds Diatomic Molecule

Metallic Bonding - “Electron Sea” RETURN Types of Bonds

Quick Hint zAll covalent bonds are between two non-metals zAll ionic bonds are between a metal (cation) and a nonmetal (anion). zAll metallic bonds are between two metals

Lewis Structure zCovalent – show sharing of electrons zIonic – show transfer of electrons

Lewis Structures zCovalent – show sharing of electrons zIonic – show transfer of electrons

Ionic Nomenclature – Ionic Formulas zWrite each ion, cation first. Don’t show charges in the final formula. zOverall charge must equal zero. yIf charges cancel, just write symbols. yIf not, use subscripts to balance charges. zUse parentheses to show more than one polyatomic ion. zStock System – Roman numerals indicate the ion’s charge

Ionic Nomenclature – Ionic Names zWrite the names of both ions, cation first. zChange ending of monatomic ions to –ide. zPolyatomic ions have special names. zStock System – Use Roman numerals to show the ion’s charge if more than one is possible. Overall charge must equal zero.

Ionic Nomenclature zConsider the following: yDoes it contain a polyatomic ion? x-ide, 2 elements  no x-ate or –ite, 3+ elements  yes yDoes it contain a Roman numeral? xCheck the table for metals not in Groups 1 or 2. yNo prefixes.

Ionic Nomenclature zPotassium chloride yK + Cl -  KCl zMagnesium nitrate yMg 2+ NO -  Mg(NO 3 ) 2 zCopper (ii) chloride yCu 2+ Cl -  CuCl 2

Ionic Nomenclature zNaBr ySodium bromide zNa 2 CO 3 ySodium carbonate zFeCl 3 yIron (III) chloride

Covalent Bonding Covalent bonds can have multiple bonds. Single Covalent Bond – Chemical bond resulting from sharing of an electron pair between two atoms

zDouble Covalent Bond yChemical bond resulting from sharing of two electron pairs between two atoms

zTriple Covalent Bonds yChemical bond resulting from sharing of three electron pairs between two atoms

Molecular Nomenclature zPrefix System (Binary system) 1.Less electronegative atom comes first. 2.Add prefixes to indicate number of atoms. Omit mono- prefix on first element. 3.Change the ending of the second element to –ide.

Molecular Nomenclature Prefixes zMono-1 zDi-2 zTri-3 zTetra-4 zPenta-5 zHexa-6 zHepta-7 zOcta-8 zNona-9 zDeca-10

Molecular Nomenclature zCCl 4 yCarbon tetrachloride zN 2 O yDinitrogen monoxide zSF 6 ySulfur hexaflouride

Molecular Nomenclature zArsenic trichloride yAsCl 3 zDinitrogen monoxide yN 2 O 5 zTetraphosphorus decoxide yP 4 O 10

Bond Polarity zMost bonds are a blend of ionic and covalent characteristics. zDifferences in electronegativity determines bond type.

Bond Polarity zElectronegativity yAttraction an atom has for a shared pair of electrons. yhigher e - neg atom   - ylower e - neg atom   +

Dipole Movement zDipole Moment - a measure of the polarity of a bond. yIs often represented by a special arrow. yArrow points to more EN atom.

Bond Polarity zElectronegativity Trend (p. 151) yIncreases up and to the right.

zNonpolar Covalent Bond ye - are shared equally ysymmetrical e - density yusually identical atoms Bond Polarity

++ -- zPolar Covalent Bond ye - are shared unequally yasymmetrical e - density yresults in partial charges (dipole)

Bond Polarity zIonic Bond ye- are not shared yresults in charged particles yopposite charges attract

Determining Type,  EN %50%

Determining Type,  EN zIonic, Polar or Nonpolar Covalent Compounds: The difference in electronegativity between bonding atoms leads to the type of compound. Example:  O 2, O=O EN O = 3.5  EN = 0   NO, N=O EN N = 3.0, EN O = 3.5  EN =.5   CO, C=  EN C = 2.5, EN O = 3.5  EN = 1.0   NaCl, Na + Cl - EN Na = 0.9, EN Cl = 3.0  EN = 2.1  Nonpolar Covalent Polar Covalent Ionic Polar Covalent

Sample Problem zUse electronegativity differences to classify bonding between sulfur, S, and the following elements: hydrogen, H; cesium, Cs; and chlorine, Cl. In each pair, which atom will be more negative? Bonding between sulfur and Electronegativity difference Bond type More-negative atom hydrogen2.5 – 2.1 = 0.4Polar-covalentsulfur cesium2.5 – 0.7 = 1.8Ionicsulfur chlorine3.0 – 2.5 = 0.5Polar-covalentchlorine

Additional Sample Problems zComplete the following chart: Elements bonded Electronegativity difference Bond type More-negative atom a. C and H2.5 – 2.1 = 0.4Polar-covalentcarbon b. C and S2.5 – 2.5 = 0Nonpolar covalent Same electronegativity c. O and H3.5 – 2.1 = 1.4Polar-covalentoxygen d. Na and Cl3.0 – 0.9 = 2.1Ionicchlorine e. Cs and S2.5 – 0.7 = 1.8Ionicsulfur