CH110 Chapter 4: Compounds & Bonds Valence Electrons & e– Dot Structures Octet Rule & Ions Ionic Compounds Covalent Compounds Molecular Shapes & Polarity 1 1

fill layers around nucleus Electron arrangement 24 12 Mg Electrons fill layers around nucleus Low  High 32 18 A new layer is added for each row or period in the table. 8 2 2n2 Shells = Energy levels

H He Be Li Ne Mg Ar Na Octet Rule 1 4 2 9 4 7 3 1 8 2 20 10 2, 1 2, 2 2, 8 24 12 Mg 40 18 Ar 23 11 Na 2, 8, 8 2, 8, 1 2, 8, 2

H Li Na K H Li Lewis Structures Show only Valence Electrons Na 1 7 3 23 11 Na K

He O F N Si S P Ca H Li C Na K Se B Ne Be Al Cl Ar Mg Kr Ga As Br Ge 1 8 H He 2 3 4 5 6 7 C O Li B N F Ne Be Si Al S Cl Ar Mg P Na Kr Ca Ga As Se Br K Ge

Na Na1+or Na+ Ions Na Metals give e-s to make Cations (+) 11 +’s 23 11 Na 11 +’s 11 -’s Na 2, 8, 1 Metals give e-s to make Cations (+) 11 +’s 10 -’s 1 + Na1+or Na+ 2, 8 = [Ne]

Cl Cl = Cl1– Cl– Ions Cl Nonmetals take e-s to make Anions (–) 17 +’s 35 17 Cl 17 +’s 17 -’s Cl 2, 8, 7 Nonmetals take e-s to make Anions (–) Cl 1- 17 +’s 18 -’s 1 - = Cl1– Cl– 2, 8, 8 = [Ar]

Na + Cl Na+ + Cl _ Formation of NaCl e– moves from Metal  Nonmetal Stable octets _ Na + Cl Na+ + Cl Metal Cation Nonmetal Anion + and - ions attract to form an ionic bond. 15 15

Ionic compounds NaCl sodium chloride Not individual molecules Form crystal arrays Ions touch many others Formula represents the average ion ratio NaCl sodium chloride Na Cl Cl Na Cl Na 18 18

Common ions Representative Elements 1+ 4+ 4- 2+ 3+ 3- 2- 1- H Li Na Cs Rb K Tl Hg Au Hf Ls Ba Fr Pt Ir Os Re W Ta He Rn At Po Bi Pb Be Mg Sr Ca Cd Ag Zr Y Pd Rh Ru Tc Mo Nb Ac Ra Zn Cu Ti Sc Ni Co Fe Mn Cr V In Xe I Te Sb Sn Ga Kr Br Se As Ge Al Ar Cl S P Si B Ne F O N C Gd Cm Tb Bk Sm Pu Eu Am Nd U Pm Np Ce Th Pr Pa Yb No Lu Lr Er Fm Tm Md Dy Cf Ho Es 2+ 3+ 3- 2- 1- 4 - 6 12 12

Na1+ Cl1- Al3+ Cl1- Cl1- Cl1- NaCl AlCl3 Ionic Formulas Metal Cations + Nonmetal Anions Na1+ Cl1- Al3+ Cl1- Cl1- Cl1- NaCl AlCl3 Sodium Chloride Aluminum Chloride

Common ions Representative Elements Transition Elements 1+ 4+ 4- 2+ 3+ H He 2+ 3+ 3- 2- 1- Transition Elements Li Be B C N O F Ne Variable Na Mg Al Si P S Cl Ar K Ca Hg Au Hf Ls Pt Ir Os Re W Ta Cd Ag Zr Y Pd Rh Ru Tc Mo Nb Ac Zn Cu Ti Sc Ni Co Fe Mn Cr V Gd Cm Tb Bk Sm Pu Eu Am Nd U Pm Np Ce Th Pr Pa Yb No Lu Lr Er Fm Tm Md Dy Cf Ho Es Ga Ge As Se Br Kr Rb Sr In Sn Sb Te I Xe Cs Ba Tl Pb Bi Po At Rn Fr Ra 12 12

Information in the table Atomic number 26 Atomic mass (weight) 55.845 Possible Charges (Valence) 2,3 Fe Elemental Symbol Electronic Configuration No longer discussed in text [Ar]3d64s2 Iron Name of the element

Fe2+ Cl1- Fe3+ Cl1- FeCl2 FeCl3 Transition Metal Ions Cl1- Cl1- Cl1- Iron(II) Chloride Iron(III) Chloride Ferrous Chloride Ferric Chloride

PO43- Na1+ SO42- Na1+ Na2SO4 (NH4)3PO4 Polyatomic Ions NH41+ NH41+ Sodium Sulfate Ammonium Phosphate

Names and Formulas of Common Polyatomic Ions

Ionic compounds Na3N NaCl Na2O MgCl2 MgO Mg3N2 AlCl3 Al2O3 AlN Some simple ions Anions Cl- O2- N3- Na+ Na3N NaCl Na2O Cations Mg2+ MgCl2 MgO Mg3N2 Al3+ AlCl3 Al2O3 AlN 17 17

Ionic compounds NaBr Na2O Na3N MgBr2 MgO Mg3N2 AlBr3 Al2O3 AlN FeBr3 Anions Br1- O2- N3- NaBr Na2O Na3N Na1+ Sodium Bromide Sodium Oxide Sodium Nitride Mg2+ MgBr2 MgO Mg3N2 Cations Magnesium Bromide Magnesium Oxide Magnesium Nitride AlBr3 Al2O3 AlN Al3+ Aluminum Bromide Aluminum Oxide Aluminum Nitride FeBr3 Fe2O3 FeN Fe3+ Iron(III) Bromide Ferric Bromide Iron(III) Oxide Ferric Oxide Iron(III) Nitride Ferric Nitride Cu1+ CuBr Cu2O Cu3N Copper(I) Bromide Cuprous Bromide Copper(I) Oxide Cuprous Oxide Copper(I) Nitride Cuprous Nitride

Thanks to Christine Neighbors (Fall 2012)

Covalent Bonds H H H + Cl Cl + Cl O O O + N N N +

Covalent Bonds H H-H H2 Cl Cl-Cl Cl2 O O=O O2 N2 N N N

O=O Covalent compounds Covalent compounds Discrete molecular units Atoms held together by bonds Covalent compounds exist in all states (CO2 - gas, H2O - liquid, SiO2 - solid) Formula represents atoms in a molecule O=O 74 74

CO C O C O CO2 O C O O=C=O Covalent Bonds Carbon monoxide Carbon dioxide O C O O=C=O May modify rules to improve the sound. Example - use monoxide not monooxide.

Naming Covalent Compounds In the names of covalent compounds, prefixes are used to indicate the number of atoms (subscript) of each element. (mono is omitted for the first element, not the second) Prefixes Used in Naming Covalent Compounds

Rules for Naming Binary Compounds Containing Two Nonmetals Write the name of the first nonmetal as it appears on the periodic table. Use a prefix if there is more than one atom. Use a prefix to indicate the number of atoms for the second nonmetal. Write the stem of the second nonmetal. Add the suffix –ide.

Naming covalent compounds Cl2O N2O5 SiO2 ICl3 P2O5 CCl4 carbon monoxide carbon dioxide dichlorine monoxide dinitrogen pentoxide silicon dioxide iodine trichloride diphosphorous pentoxide carbon tetrachloride May modify rules to improve the sound. Example - use monoxide not monooxide. 34 34

Bond Polarity, Electronegativity H Cl Cl H Electrons in covalent bonds rarely get shared equally.

Electronegativity Cl H Relative ability of atoms to attract e-. 1.0 Br Cl Po Te Se S Bi Sb As P Pb Sn Ge Si F O N Tl Na Cs Rb K Ba Mg Sr Ca In Ga Al H Li Be B C 1.0 0.8 0.9 1.5 1.2 0.7 2.0 1.6 1.7 1.8 2.5 1.9 3.0 2.1 3.5 2.4 4.0 2.8 66 66

H Cl – + Bond Polarity, Electronegativity Cl H This unequal sharing results in polar bonds. + – H Cl Slight positive side Smaller electronegativity Slight negative Larger electronegativity 67 67

H Cl – Bond Polarity, Electronegativity Cl H + This unequal sharing results in polar bonds. – + H Cl Slight positive side Smaller electronegativity Slight negative side Larger electronegativity

Bond Polarity, Electronegativity Difference < 0.5 Nonpolar 0.5-1.7 Polar >1.8 Ionic Cl H 2.1 3.0 H Cl d+ d– Polar Covalent

O=C=O Polarity, Shape O C O d– d+ d– CO2 Electronegativity Difference < 0.5 Nonpolar 0.5-1.7 Polar >1.8 Ionic O C O 3.5 2.5 3.5 O=C=O d– d+ d– Polar Covalent Bonds Linear Shape (180o) Nonpolar Compound

Polar and Non-Polar Thanks to Paula H. & Judy M. (Summer 1976)

O=C=O Polarity, Shape Linear d– d+ d– Nonpolar Compound d– e–’s in 2 directions = 180o O=C=O Linear d– d+ d– Nonpolar Compound e–’s in 3 directions = 120o d– Trigonal planar Polar Compound d+

Polarity, Shape C H Cl C H Cl O H H-O-H d+ d– Tetrahedral d+ d– d+ e–’s in 4 directions = 109.5o C H Cl C H Cl d+ d– Tetrahedral d+ 4 directions = 109.5o O H d– d+ H-O-H Bent

Polarity, Shape N H N H d- d+ d+ d+ Pyramidal e–’s in 4 directions = 109.5o d- N H N H d+ d+ d+ Pyramidal

Some common geometries e- directions around Shape central atom Example___ Linear 2 O=C=O Trigonal Planar 3 Tetrahedral 4

Tetrahedral electron-pair Geometries Bent Pyramidal Tetrahedral H    O 109.5º N C H H H H H H 105º H H 107º Water, H2O 2 bond pairs Ammonia, NH3 3 bond pairs Methane, CH4 4 bond pairs

Molecular geometry Molecules have specific shapes. Determined by the number of electron pairs around the central atom Bonded and unbonded pairs Geometry affects factors like polarity and solubility. 55 55

Geometry and polar molecules For a molecule to be polar - must have polar bonds - must have the proper geometry CH4 non-polar CH3Cl polar CH2Cl2 polar CHCl3 polar CCl4 non-polar WHY? 68 68

Polarity and solubility Solubility The maximum amount of a solute that dissolves in a given solvent Depends on the forces of attraction between molecules - intermolecular Types of intermolecular attractions most often encountered Dipole-Dipole Hydrogen bonding Van der Wall forces General rule “Like dissolves like” 69 69

Boiling and melting points Chemical Bond Mp Bp N2 Nonpolar -210 -196 O2 Nonpolar -219 -183 NH3 Polar -78 -33 H2O Polar 0 100 NaCl Ionic 804 ? Melting and Boiling points Very high for ionic compounds Typically lower for covalent compounds 77 77