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Chapter 4 Compounds and Their Bonds

Chapter 4 Compounds and Their Bonds. 4.5 Covalent Bonds 4.6 Naming and Writing Formulas of Covalent Compounds 4.7 Bond Polarity. Covalent Bonds. Covalent bonds form between two nonmetals from Groups 4A, 5A, 6A, and 7A. In a covalent bond, electrons are shared to complete octets.

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Chapter 4 Compounds and Their Bonds

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  1. Chapter 4 Compounds and Their Bonds 4.5 Covalent Bonds 4.6 Naming and Writing Formulas of Covalent Compounds 4.7 Bond Polarity

  2. Covalent Bonds • Covalent bonds form between two nonmetals from Groups 4A, 5A, 6A, and 7A. • In a covalent bond, electrons are shared to complete octets.

  3. Learning Check Indicate whether a bond between the following is 1) Ionic 2) Covalent ____A. sodium and oxygen ____B. nitrogen and oxygen ____C. phosphorus and chlorine ____D. calcium and sulfur ____E. chlorine and bromine

  4. Solution Indicate whether a bond between the following is 1) Ionic 2) Covalent 1 A. sodium and oxygen 2 B. nitrogen and oxygen 2 C. phosphorus and chlorine 1 D. calcium and sulfur 2 E. chlorine and bromine

  5. H2, A Covalent Molecule • In hydrogen, two hydrogen atoms share their electrons to form a covalent bond. • Each hydrogen atom acquires a stable outer shell of two (2) electrons like helium (He). H+H H : H = HH = H2 hydrogen molecule

  6. Diatomic Elements • As elements, the following share electrons to form diatomic, covalent molecules.

  7. Learning Check What is the name of each of the following diatomic molecules? H2 hydrogen N2 nitrogen Cl2 _______________ O2 _______________ I2 _______________

  8. Solution What are the names of each of the following diatomic molecules? H2 hydrogen N2 nitrogen Cl2chlorine O2oxygen I2iodine

  9. Covalent Bonds in NH3 • The compound NH3 consists of a N atom and three H atoms.   N and 3 H  • By sharing electrons to form NH3, the electron dot structure is written as H Bonding pairs   H : N : H  Lone pair of electrons

  10. Number of Covalent Bonds • Often, the number of covalent bonds formed by a nonmetal is equal to the number of electrons needed to complete the octet.

  11. Dot Structures and Models of Some Covalent Compounds

  12. Multiple Bonds • Sharing one pair of electrons is a single bond.X : X or X–X • In multiple bonds, two pairs of electrons are shared to form a double bond or three pairs of electrons are shared in a triple bond.X : : X or X =XX ::: X or X ≡X

  13. Multiple Bonds in N2 • In nitrogen, octets are achieved by sharing three pairs of electrons. • When three pairs of electrons are shared, the multiple bond is called a triple bond. octets       N  + N  N:::N  triple bond

  14. Naming Covalent Compounds • In the name of a covalent compound, the first nonmetal is named followed by the name of the second nonmetal ending in –ide. • Prefixes indicate the number of atoms of each element.

  15. Learning Check Complete the name of each covalent compound: CO carbon ______oxide CO2 carbon _______________ PCl3 phosphorus ___________ CCl4 carbon _______________ N2O ______________________

  16. Solution Complete the name of each covalent compound: CO carbon monoxide CO2 carbon dioxide PCl3 phosphorus trichloride CCl4 carbon tetrachloride N2O dinitrogen monoxide

  17. Formulas and Names of Some Covalent Compounds

  18. Learning Check Select the correct name for each compound. A. SiCl4 1) silicon chloride 2) tetrasilicon chloride 3) silicon tetrachloride B. P2O5 1) phosphorus oxide 2) phosphorus pentoxide 3) diphosphorus pentoxide C. Cl2O7 1) dichlorine heptoxide 2) dichlorine oxide 3) chlorine heptoxide

  19. Solution Select the correct name for each compound. A. SiCl43) silicon tetrachloride B. P2O53) diphosphorus pentoxide C. Cl2O7 1) dichlorine heptoxide

  20. Electronegativity • Electronegativity is the attraction of an atom for shared electrons. • The nonmetals have high electronegativity values with fluorine as the highest. • The metals have low electronegativity values.

  21. Some Electronegativity Values for Group A Elements

  22. Nonpolar Covalent Bonds • The atoms in a nonpolar covalent bond have electronegativity differences of 0.3 or less. • Examples: Atoms Electronegativity Type of Difference Bond N-N3.0 - 3.0 = 0.0 Nonpolar covalentCl-Br3.0 - 2.8 = 0.2 Nonpolar covalentH-Si 2.1 - 1.8 = 0.3 Nonpolar covalent

  23. Polar Covalent Bonds • The atoms in a polar covalent bond have electronegativity differences of 0.4 to 1.6. • Examples: Atoms Electronegativity Type of Difference BondO-Cl3.5 - 3.0 = 0.5 Polar covalentCl-C3.0 - 2.5 = 0.5 Polar covalentO-S 3.5 - 2.5= 1.0 Polar covalent

  24. Comparing Nonpolar and Polar Covalent Bonds

  25. Ionic Bonds • The atoms in an ionic bond have electronegativity differences of 1.7 or more. • Examples: Atoms Electronegativity Type of Difference BondCl-K3.0 – 0.8 = 2.2 IonicN-Na3.0 – 0.9 = 2.1 IonicS-Cs 2.5 – 0.7 = 1.8 Ionic

  26. Range of Bond Types

  27. Predicting Bond Type

  28. Learning Check Identify the type of bond between the following as 1) nonpolar covalent 2) polar covalent 3) ionic A. K-N B. N-O C. Cl-Cl

  29. Solution A. K-N 3) ionic B. N-O 2) polar covalent C. Cl-Cl 1) nonpolar covalent

  30. Chapter 4 Compounds and Their Bonds 4.8 Polyatomic Ions

  31. Polyatomic Ions • A polyatomic ion is a group of two or more atoms that has an overall ionic charge. • Some examples of polyatomic ions are NH4+ ammonium OH - hydroxide NO3- nitrate NO2 - nitrite CO32 - carbonate PO43 - phosphate HCO3 - hydrogen carbonate (bicarbonate)

  32. Common Polyatomic Ions

  33. Formulas with Polyatomic Ions • The formula of an ionic compound containing a polyatomic ion is written to make the overall charge equal zero (0). Na+ and NO3- NaNO3 • When two or more polyatomic ions are needed, the polyatomic ion is enclosed in parentheses. polyatomic ion Mg2+ and NO3 - Mg(NO3)2 subscript 2 for charge balance

  34. Some Compounds with Polyatomic Ions

  35. Learning Check Select the correct formula for each: A. Aluminum nitrate 1) AlNO3 2) Al(NO)3 3) Al(NO3)3 B. Copper(II) nitrate 1) CuNO3 2) Cu(NO3)2 3) Cu2(NO3) C. Iron (III) hydroxide 1) FeOH 2) Fe3OH 3) Fe(OH)3 D. Tin(IV) hydroxide 1) Sn(OH)4 2) Sn(OH)2 3) Sn4(OH)

  36. Solution Select the correct formula for each: A. Aluminum nitrate 3) Al(NO3)3 B. Copper(II) nitrate 2) Cu(NO3)2 C. Iron (III) hydroxide 3) Fe(OH)3 D. Tin(IV) hydroxide 1) Sn(OH)4

  37. Naming Compounds with Polyatomic Ions • For compounds with polyatomic ions, the positive ion is named first followed by the name of the polyatomic ion.NaNO3 sodium nitrateK2SO4potassium sulfateAl(HCO3)3aluminumbicarbonate oraluminum hydrogen carbonate(NH4)3PO4 ammonium phosphate

  38. Learning Check Match each formula with the correct name: A.Na2CO3 1) magnesium sulfite MgSO3 2) magnesium sulfate MgSO4 3) sodium carbonate B. Ca(HCO3)2 1) calcium carbonate CaCO3 2) calcium phosphate Ca3(PO4)2 3) calcium bicarbonate

  39. Solution A.Na2CO33) sodium carbonate MgSO31) magnesium sulfite MgSO42) magnesium sulfate B. Ca(HCO3)23) calcium bicarbonate CaCO31) calcium carbonate Ca3(PO4)2 2) calcium phosphate

  40. Summary of Naming Compounds

  41. Naming Rules

  42. Naming Rules (continued)

  43. Learning Check Name each of the following compounds: A. Mg(NO3)2 B. CuCl2 C. N2O4 D. Fe2(SO4)3 E. Ba3(PO4)2

  44. Solution Name each of the following compounds: A. Mg(NO3)2 magnesium nitrate B. CuCl2 copper(II) chloride C. N2O4 dinitrogen tetroxide D. Fe2(SO4)3 iron(III) sulfate E. Ba3(PO4)2 barium phosphate

  45. Learning Check Write the correct formula for each: A. potassium sulfide B. calcium carbonate C. sodium phosphite D. iron(III) oxide E. iron (II) nitrate

  46. Solution Write the correct formula for each: A. potassium sulfide K2S B. calcium carbonate CaCO3 C. sodium phosphite Na3PO3 D. iron(III) oxide Fe2O3 E. iron (II) nitrate Fe(NO3)2

  47. Chapter 4 Compounds and Their Bonds 4.9 Shapes of Molecules 4.10 Polar and Nonpolar Molecules

  48. VSEPR • The shape of a molecule is predicted from the geometry of the electrons pairs around the central atom. • In the valence-shell electron-pair repulsion theory (VSEPR), the electron pairs are arranged as far apart as possible to give the least amount of repulsion of the negatively charged electrons.

  49. Two Electron Pairs • In a molecule of BeCl2, there are two bonding pairs around the central atom Be. (Be is an exception to the octet rule.) • The arrangement of two electron pairs to minimize their repulsion is 180° or opposite each other. • The shape of the molecule is linear.

  50. Two Electron Pairs with Double Bonds • The electron-dot structure for CO2 consists of two double bonds to the central atom C. • Because the electrons in a double bond are held together, a double bond is counted as a single unit. • Repulsion is minimized when the double bonds are placed opposite each other at 180° to give a linear shape.

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