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Chemeketa Community College
Chapter 4: Compounds & Bonds Larry Emme Chemeketa Community College
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Valence Electrons & e– Dot Structures Molecular Shapes & Polarity
Chapter Outline Valence Electrons & e– Dot Structures Octet Rule & Ions Ionic Compounds Covalent Compounds Molecular Shapes & Polarity 1 1
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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
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IA IIA 1 H 4 2 He 7 3 Li 9 4 Be 2, 1 2, 2
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IA IIA IIIA 1 H 11 5 B 7 3 Li 9 4 Be 2, 1 2, 2 2, 3
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IIIA IVA VA 11 5 B 12 6 C 13 7 N 2, 3 2, 4 2, 5
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H He Be Li Ne Mg Ar Na 1 4 2 9 7 4 3 IA IIA VIIIA 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
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H Be Li B Mg Al Na 1 9 7 4 3 1 Valence electrons Where most chemical
Reactions occur. 1 H 2 3 9 4 Be 7 3 Li 11 5 B 2, 3 2, 1 2, 2 24 12 Mg 27 13 Al 23 11 Na 2, 8, 3 2, 8, 1 2, 8, 2
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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
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H Li Na K H Li Lewis Structures Show only Valence Electrons Na 1 7 3
23 11 Na K
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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
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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]
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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]
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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
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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
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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
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Na1+ Cl1- Al3+ Cl1- Cl1- Cl1- NaCl AlCl3 Ionic Formulas
Metal Cations + Nonmetal Anions Na1+ Cl1- Al3+ Cl1- Cl1- Cl1- Drop charges NaCl AlCl3 Sodium Chloride Write metal first Aluminum Chloride
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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
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Information in the table
Atomic number 26 Atomic mass (weight) 55.845 2,3 Possible Charges (Valence) Fe Elemental Symbol Iron Name of the element
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Fe2+ Cl1- Fe3+ Cl1- FeCl2 FeCl3 Transition Metal Ions Cl1- Cl1- Cl1-
Iron(II) Chloride Iron(III) Chloride Ferrous Chloride Ferric Chloride
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PO43- Na1+ SO42- Na1+ Na2SO4 (NH4)3PO4 Polyatomic Ions NH41+ NH41+
Sodium Sulfate Ammonium Phosphate
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Names and Formulas of Common Polyatomic Ions
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Ionic compounds Some simple ions Anions Cl- O2- N3- Na+ Cations Mg2+
Al3+ 17 17
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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
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Ionic compounds Anions Br1- O2- N3- Na1+ Mg2+ Cations Al3+ Fe3+ Cu1+
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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
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Covalent Bonds H H H + Cl Cl + Cl O O O + N N N +
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Covalent Bonds H H-H H2 Cl Cl-Cl Cl2 O O=O O2 N2 N N N
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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
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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.
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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
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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 ALWAYS If the second nonmetal begins in an “o”, drop the prefix “a” or “o”. Write the stem of the second nonmetal. Add the suffix –ide.
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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
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Bond Polarity, Electronegativity
H Cl Cl H Electrons in covalent bonds rarely get shared equally.
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Electronegativity Cl H
Relative ability of atoms to attract shared e-s. At I 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
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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
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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
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Bond Polarity, Electronegativity
Difference < 0.5 Nonpolar Polar >1.8 Ionic Cl H 2.1 3.0 H Cl d+ d– Polar Covalent
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O=C=O Polarity, Shape O C O d– d+ d– CO2 Electronegativity Difference
< 0.5 Nonpolar 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
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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+
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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
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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
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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
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Some common geometries
e- directions around Shape central atom Example___ Linear O=C=O Trigonal Planar 3 Tetrahedral 4
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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
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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
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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
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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
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Boiling and melting points
Chemical Bond Mp Bp N2 Nonpolar O Nonpolar NH Polar H2O Polar NaCl Ionic ? Melting and Boiling points Very high for ionic compounds Typically lower for covalent compounds 77 77
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The End
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End of Chapter Learning Checks Try these after you have reviewed the chapter
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Learning Check The element potassium is in the first group on the Periodic Table (group IA). Potassium is a. an alkali metal b. an alkaline earth metal c. a transition element d. a halogen
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Learning Check Answers
The element potassium is in the first group on the Periodic Table (group IA). Potassium is a. an alkali metal b. an alkaline earth metal c. a transition element d. a halogen
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Learning Check Which of the following is not likely to be a molecule?
CaCl2 NH3 CO2 SF6
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Learning Check Answers
Which of the following is not likely to be a molecule? CaCl2 NH3 CO2 SF6
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Learning Check Which of the following is true?
Metals form anions with negative charges. Metals form anions with positive charges. Metals form cations with positive charges. Metals form cations with negative charges.
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Learning Check Answers
Which of the following is true? Metals form anions with negative charges. Metals form anions with positive charges. Metals form cations with positive charges. Metals form cations with negative charges.
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Learning Check Which is not a physical property of aluminum?
Aluminum is silver and has luster. The melting point of aluminum is 660º C. Aluminum reacts with acid to produce an aluminum salt and hydrogen gas. The density of aluminum at 25º C is 2.70 g/cm3.
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Learning Check Answers
Which is not a physical property of aluminum? Aluminum is silver and has luster. The melting point of aluminum is 660º C. Aluminum reacts with acid to produce an aluminum salt and hydrogen gas. The density of aluminum at 25º C is 2.70 g/cm3.
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Learning Check Which property of acetone is a chemical property?
The specific gravity of acetone is 0.79. The boiling point of acetone is 56°C. Acetone is a clear, colorless liquid Acetone is a flammable liquid.
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Learning Check Answers
Which property of acetone is a chemical property? The specific gravity of acetone is 0.79. The boiling point of acetone is 56°C. Acetone is a clear, colorless liquid Acetone is a flammable liquid.
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Learning Check Which is a chemical change? Dry ice sublimes
A penny tarnishes Ice cream melts Rock is ground into sand
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Learning Check Answers
Which is a chemical change? Dry ice sublimes A penny tarnishes Ice cream melts Rock is ground into sand
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Learning Check What is the correct formula for the compound silver sulfide? AgS AgS2 Ag2S 2AgS
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Learning Check Answers
What is the correct formula for the compound silver sulfide? AgS AgS2 Ag2S 2AgS
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Learning Check What is the correct name for CdF2? Cadmium flourine
Cadmium flouride Cadmium fluorine Cadmium fluoride
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Learning Check Answers
What is the correct name for CdF2? Cadmium flourine Cadmium flouride Cadmium fluorine Cadmium fluoride
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Learning Check CuCl2 is Copper chloride Copper (I) chloride
Copper (II) chloride Cuprous chloride Copper chloride (II)
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Learning Check Answers
CuCl2 is Copper chloride Copper (I) chloride Copper (II) chloride Cuprous chloride Copper chloride (II)
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Learning Check HgS is mercury(II) sulfide mercury(I) sulfide
mercury sulfide mercurous sulfide
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Learning Check Answers
HgS is mercury(II) sulfide mercury(I) sulfide mercury sulfide mercurous sulfide
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Learning Check Arsenic pentachloride is AsCl5 As5Cl As2Cl5 AsCl
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Learning Check Answers
Arsenic pentachloride is AsCl5 As5Cl As2Cl5 AsCl
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Learning Check Sulfur dioxide is SO S2O SO2
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Learning Check Answers
Sulfur dioxide is SO S2O SO2
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Learning Check Sulfate is SO42-. Name the compound FeSO4. iron sulfate
iron(I) sulfate iron(II) sulfate iron(IV) sulfate
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Learning Check Answers
Sulfate is SO42-. Name the compound FeSO4. iron sulfate iron(I) sulfate iron(II) sulfate iron(IV) sulfate
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Learning Check A polar covalent bond will form between which two atoms? Beryllium and fluorine Hydrogen and chlorine Sodium and oxygen Fluorine and fluorine
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Learning Check Answers
A polar covalent bond will form between which two atoms? Beryllium and fluorine Hydrogen and chlorine Sodium and oxygen Fluorine and fluorine
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Learning Check What is the molecular geometry for CO2? linear
trigonal planar tetrahedral trigonal pyramidal bent
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Learning Check Answers
What is the molecular geometry for CO2? linear trigonal planar tetrahedral trigonal pyramidal bent
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