Unit 4 Bonding II Review Unit 4 Bonding II Determine the type of bond (, or Metallic) in the following compounds: Compound Bond Type Compound Bond Type NaCl CO FeNi SiS 2 Metallic NCl 3 PF 3 CaCl 2 Fe 2 O 3 Draw the Lewis Structures 1) PBr 3 4) NO 1 2 Draw the Lewis Structures 1) PBr 3 4) NO 1 2 [ ] 1 2) N 2 H 2 5) C 2 H 4 2) N 2 H 2 5) C 2 H 4 3) CH 3 OH 6) HBr 3) CH 3 OH 6) HBr 1
Rules of writing formulas: 1. Positive ion is written first this is usually a metal 2. Negative ion is written second this is usually a nonmetal 3. Subscripts are used to show how many ions of each part are in the compound. They are used to balance the charge of the ions. The overall charge should be 0 Criss-cross method: Examples: 1. Sodium oxide * sodium is the positive ion = +1 * oxide is the negative ion = -2 * therefore it takes 2 sodium ions to balance the charge of the oxide Formula = Na 2 O Rules of writing formulas: 2. Calcium nitrate calcium is the positive ion = +2 nitrate is the negative ion = -1 therefore it takes 2 nitrates to balance the charge of calcium Formula = Ca(NO 3 ) 2 3. Aluminum sulfide aluminum is the positive ion = +3 sulfide is the negative ion = -2 therefore it takes 2 aluminum ions and 3 sulfide to balance the charge Formula = Al 2 S 3 Unit 4 Bonding II Write the correct formulas for each covalent compound: Compound Name Oxidation States Formula Naming Binary covalent compounds are characterized by having two nonmetals. Naming these compounds involves the use of numerical prefixes: Water Carbon Dioxide Prefix Number Prefix Number mono- 1 hexa- 6 di- 2 hepta- 7 tri- 3 octa- 8 tetra- 4 nona- 9 penta- 5 deca- 10 Chlorine (Diatomic Element) Cl (1) Methane (5 N (3) Ammonia (4 Carbon tetrabromide (5 total atoms) Br (1) Phosphorous trichloride (4 Diphosphorous trioxide (5 Cl (1) 2
Write the correct formulas for each covalent compound: Compound Name Oxidation States Formula Write the correct formulas for each covalent compound: Compound Name Oxidation States Formula Water H 2 0 Water H 2 0 Carbon Dioxide CO 2 Carbon Dioxide CO 2 Chlorine (Diatomic Element) Cl (1) Chlorine (Diatomic Element) Cl (1) Cl 2 Methane (5 Methane (5 CH 4 Ammonia (4 N (3) Ammonia (4 N (3) Carbon tetrabromide (5 total atoms) Br (1) Carbon tetrabromide (5 total atoms) Br (1) Phosphorous trichloride (4 Cl (1) Phosphorous trichloride (4 Cl (1) Diphosphorous trioxide (5 Diphosphorous trioxide (5 Write the correct formulas for each covalent compound: Compound Name Oxidation States Formula Unit 4 Bonding II Water Carbon Dioxide H 2 0 CO 2 Determine the type of bond (, or Metallic) in the following compounds: Compound Bond Type Compound Bond Type Chlorine (Diatomic Element) Cl (1) Cl 2 Methane (5 Ammonia (4 CH 4 N (3) NaCl CO FeNi SiS 2 Metallic NCl 3 PF 3 CaCl 2 Fe 2 O 3 Carbon tetrabromide (5 total atoms) Br (1) CBr 4 Phosphorous trichloride (4 Diphosphorous trioxide (5 Cl (1) PCl 3 P 2 O 3 3
Balancing Charges: Criss Cross rule * Write out symbols and charge of elements * Criss Cross charges as subscripts (Swap and Drop) * Combine as a formula unit Equation Form of Balancing Charges (Number of Cations)x(Cation Charge) + (Number of Anions)x(Anion Charge) = 0 EX: Aluminum and Oxygen EX: Barium and Oxygen Al 3+ O 2 Ba 2+ O 2 Balancing Charges Practice Lithium Iodide Li +1 I 1 so LiI Strontium Chloride Sr +2 Cl 1 so SrCl 2 Sodium Sulfide Na +1 S 2 so Na 2 S AL 2 O 3 BaO Lithium Iodide (LiI) Strontium Chloride (SrCl 2 ) Sodium Sulfide (Na 2 S) Balancing Charges Practice Balancing Charges Practice Mg +2 Cs + Cr +3 Na Zn +2 Cl S 2 F N 3 O P 3 Cl S 2 F N 3 O P 3 Mg +2 MgCl 2 MgS MgF 2 Mg 3 N 2 MgO Mg 3 P 2 Cs + CsCl Cs 2 S CsF Cs 3 N Cs 2 O Cs 3 P Cr +3 CrCl 3 Cr 2 S 3 CrF 3 CrN Cr 2 O 3 CrP Na NaCl Na 2 S NaF Na 3 N Na 2 O Na 3 P Zn +2 ZnCl 2 ZnS ZnF 2 Zn 3 N 2 ZnO Zn 3 P 2 Al +3 K Al +3 AlCl 3 Al 2 S 3 AlF 3 AlN Al 2 O 3 AlP K KCl K 2 S KF K 3 N K 2 O K 3 P 4
Valence Shell Electron Pair Repulsion Theory This is the way that we predict the geometry shape of molecules, A model was developed a qualitative model known as Valence Shell Electron Pair Repulsion Theory (_VSEPR Theory). The basic assumptions of this theory are summarized below. 1) The electron pairs in the valence shell around the central atom of a molecule repel each other and tend to orient in space so as to minimize the repulsions and maximize the distance between them. 2) There are two types of valence shell electron pairs: Bonded pairs and Unbonded pairs Bond pairs are Electrons shared by two atoms and are attracted by two nuclei. Hence they occupy less space and cause less repulsion. Lone pairs are pairs of electrons not involved in bond formation and are in attraction with only one nucleus. Hence they occupy more space. As a result, the lone pairs cause more repulsion. Note: The bond pairs are usually represented by a _line drawn between the two atoms_, whereas the lone pairs are represented by a lobe with two electrons. Valence Shell Electron Pair Repulsion Theory 3) In VSEPR theory, the _double and triple_ bonds are treated as if they were single bonds. The electron pairs in multiple bonds are treated collectively as a single super pair. 4) The shape of a molecule can be predicted from the number and type of valence shell electron pairs around the central atom. When the valence shell of central atom contains only bond pairs, the molecule assumes symmetrical geometry due to even repulsions between them. Unit 4 Bonding 5
Unit 5 Bonding VSEPR Practice Complete the table with the requested information. Molecule Structural Diagram Oxidation State of each element CClF 3 CL (1) F (1) Molecular Geometry SF 2 Steric number is the total number of atoms bonded to the central atom and plus the number of lone pairs on the central atom. BF 3 SiBr 4 VSEPR Practice Complete the table with the requested information. Polyatomic Ions Molecule Structural Diagram Oxidation State of each element CClF 3 CL (1) F (1) SF 2 S (2) F (1) BF 3 B (3) F (1) SiBr 4 Si (4) Br(1) Molecular Geometry Polyatomic ions are groups of atoms that are covalently bonded, but carry an overall net charge. The names of polyatomic ions must be memorized to appropriately name these compounds. N (3) 6
Polyatomic Ions Polarity ClO 3 Chlorate Bond Polarity Electronegativity bonds have an electronegativity difference that is greater than 1.7. bonds have an electronegativity difference less than (or equal to) 1.7. Electronegativity differences between 0 and 0.4 indicate non polar covalent bonds. Electronegativity differences between 0.4 and 1.7 indicate polar covalent bonds. Polar Bond a covalent bond in which the electrons are not shared equally because one atom attracts them more strongly than the other. Non polar Bond a covalent bond in which the electrons are shared equally. Use the periodic table of electronegativities to answer the questions on electronegativity differences. Electronegativity Electronegativity H 2.1 Li 1.0 Na 0.9 Be 1.5 ELECTRONEGATIVITY Mg (electron attraction!) 1.2 B 2.0 Al 1.5 C 2.5 Si N 3.0 P 2.1 O 3.5 S 2.5 F 4.0 Cl 3.0 Determine the type of bond that would form between the following two elements using differences in electronegativity. K 0.8 Rb 0.8 Cs 0.7 Fr 0.7 Ca 1.0 Sr 1.0 Ba 0.9 Ra 0.9 Sc 1.3 Y 1.2 La Lu 1.0 1.2 Ac 1.1 Ti 1.5 Zr 1.4 Hf 1.3 Th 1.3 V Nb Ta 1.5 Pa 1.4 Cr Mo W 1.7 U 1.4 Mn 1.5 Tc Re Np No 1.4 1.3 Fe Ru Os Co Rh Ir Ni Pd Pt Cu Ag Au 2.4 Zn Cd 1.7 Hg Ga In 1.7 Tl Ge Sn Pb As 2.0 Sb Bi Se 2.4 Te 2.1 Po 2.0 Br 2.8 I 2.5 At Example: Mg O O is 3.5 and Mg is 1.2, therefore, the difference is 3.5 1.2 = 2.3 IONIC Example: Cl Cl Cl is 3.0. The difference is 3.0 3.0 = 0 NON POLAR COVALENT 7
Electronegativity Bond Electronegativity Difference Bond Type Electronegativity Bond Electronegativity Difference Bond Type 1. C N 2. Li F 1. C N 0.5 Polar 2. Li F 3.0 Bond Electronegativity Difference Bond Type Bond Electronegativity Difference Bond Type 3. N Cl 4. Na Cl 5. O F 6. B H 7. Ba F 8. C H 3. N Cl 0.0 4. Na Cl 2.1 5. O F 0.5 Polar 6. B H 0.1 7. Ba F 3.1 8. C H 0.4 Molecular Polarity Dipole moment a property of a molecule whereby the charge distribution can be represented by a center of positive charge and a center of negative charge. Polar Molecule a molecule that has a permanent dipole moment. Determining if a molecule is polar. If ALL of the bonds are non polar, then the molecule is non polar. If some or all of the bonds are polar, you can consider the vectors. Vectors are arrows that point in the direction of the negative charge (the direction the electrons are pulled). Examples: Molecular Polarity 8
Molecular Polarity Structural formula Polar or non polar Formula *Diagram Formula Polar/Non polar SCl 2 CF 4 PCl 3 H 2 S C 2 H 2 * Bent must be draw as bent Structural formula Polar or non polar Formula *Diagram Formula Polar/Non polar Polar SCl 2 Polar CF 4 Non Polar PCl 3 Polar H 2 S Polar C 2 H 2 NonPolar * Bent must be draw as bent 9