Chapter4
- 1. Chapter 4 Chemical Bonding: The Ionic Bond Model
- 2. Chapter 4 Table of Contents 4.1Chemical Bonds 4.2Valence Electrons and Lewis Symbols 4.3The Octet Rule 4.4The Ionic Bond Model 4.5The Sign and Magnitude of Ionic Charge 4.6Lewis Structures for Ionic Compounds 4.7Chemical Formulas for Ionic Compounds 4.8The Structure of Ionic Compounds 4.9Recognizing and Naming Binary Ionic Compounds 4.10Polyatomic Ions 4.11Chemical Formulas and Names for Ionic Compounds Con Copyright © Cengage Learning. All rights reserved 2
- 3. Section 4.1 Chemical Bonds A Chemical Bond • Attractive force that holds two atoms together in a more complex unit. • Form as a result of interactions between electrons found in the combining atoms. Return to TOC Copyright © Cengage Learning. All rights reserved 3
- 4. Section 4.1 Chemical Bonds Two Types of Chemical Bonds • Ionic Bonds • Covalent Bonds Return to TOC Copyright © Cengage Learning. All rights reserved 4
- 5. Section 4.1 Chemical Bonds Ionic Bond • Chemical bond formed through the transfer of one or more electrons from one atom or group of atoms to another atom or group of atoms. • Ionic Compound – A compound in which ionic bonds are present. Return to TOC Copyright © Cengage Learning. All rights reserved 5
- 6. Section 4.1 Chemical Bonds Covalent Bond • Chemical bond formed through the sharing of one or more pairs of electrons between two atoms. • Molecular Compound (Covalent Compound) – A compound in which atoms are joined through covalent bonds. Return to TOC Copyright © Cengage Learning. All rights reserved 6
- 7. Section 4.1 Chemical Bonds Bonding • Most bonds are not 100% ionic or 100% covalent. • Most bonds have some degree of both ionic and covalent character. Return to TOC Copyright © Cengage Learning. All rights reserved 7
- 8. Section 4.1 Chemical Bonds Two Fundamental Concepts 1. Not all electrons in an atom participate in bonding. Those that participate are called valence electrons. 2. Certain arrangements of electrons are more stable than others, as is explained by the octet rule. Return to TOC Copyright © Cengage Learning. All rights reserved 8
- 9. Section 4.2 Valence Electrons and Lewis Symbols Valence Electron • An electron in the outermost electron shell of a representative element or noble-gas element. • Valence electrons are found in either s or p subshells. Return to TOC Copyright © Cengage Learning. All rights reserved 9
- 10. Section 4.2 Valence Electrons and Lewis Symbols Lewis Symbol • Chemical symbol of an element surrounded by dots equal in number to the number of valence electrons present in atoms of the element. Return to TOC Copyright © Cengage Learning. All rights reserved 10
- 11. Section 4.2 Valence Electrons and Lewis Symbols Lewis Symbols for Selected Representative and Noble-Gas Elements Return to TOC Copyright © Cengage Learning. All rights reserved 11
- 12. Section 4.2 Valence Electrons and Lewis Symbols Concept Check Determine the number of valence electrons in each of the following elements: Ca 2 valence electrons (4s2) Se 6 valence electrons (4s24p4) C 4 valence electrons (2s22p2) Return to TOC Copyright © Cengage Learning. All rights reserved 12
- 13. Section 4.2 Valence Electrons and Lewis Symbols Three Important Generalizations 1. Representative elements in the same group have the same number of valence electrons. 2. The number of valence electrons for representative elements is the same as the Roman numeral periodic-table number. 3. The maximum number of valence electrons for any element is eight. Return to TOC Copyright © Cengage Learning. All rights reserved 13
- 14. Section 4.2 Valence Electrons and Lewis Symbols Concept Check Write Lewis symbols for the following elements: O O P P F F Return to TOC Copyright © Cengage Learning. All rights reserved 14
- 15. Section 4.3 The Octet Rule • Certain arrangements of valence electrons are more stable than others. • The valence electron configurations of the noble gases are considered the most stable of all valence electron configurations. Return to TOC Copyright © Cengage Learning. All rights reserved 15
- 16. Section 4.3 The Octet Rule Octet Rule • In forming compounds, atoms of elements lose, gain, or share electrons in such a way as to produce a noble-gas electron configuration for each of the atoms involved. Return to TOC Copyright © Cengage Learning. All rights reserved 16
- 17. Section 4.4 The Ionic Bond Model Ion • An atom (or group of atoms) that is electrically charged as a result of the loss or gain of electrons. • If an atom gains one or more electrons, it becomes a negatively charged ion. • If an atom loses one or more electrons, it becomes a positively charged ion. Return to TOC Copyright © Cengage Learning. All rights reserved 17
- 18. Section 4.4 The Ionic Bond Model Return to TOC Copyright © Cengage Learning. All rights reserved 18
- 19. Section 4.4 The Ionic Bond Model Concept Check Give the chemical symbol for each of the following ions. a) The ion formed when a potassium atom loses one electron. K+ c) The ion formed when a sulfur atom gains two electrons. S2– Return to TOC Copyright © Cengage Learning. All rights reserved 19
- 20. Section 4.5 The Sign and Magnitude of Ionic Charge • Atoms tend to gain or lose electrons until they have obtained an electron configuration that is the same as that of a noble gas. Example: K+ (1s22s22p63s23p6) Lost one electron to obtain electron configuration for Ar (1s22s22p63s23p6). Return to TOC Copyright © Cengage Learning. All rights reserved 20
- 21. Section 4.5 The Sign and Magnitude of Ionic Charge 1. Metal atoms containing one, two, or three valence electrons tend to lose electrons to acquire a noble-gas electron configuration. Group Charge IA 1+ IIA 2+ IIIA 3+ Return to TOC Copyright © Cengage Learning. All rights reserved 21
- 22. Section 4.5 The Sign and Magnitude of Ionic Charge 2. Nonmetal atoms containing five, six, or seven valence electrons tend to gain electrons to acquire a noble-gas electron configuration. Group Charge VIIA 1– VIA 2– VA 3– Return to TOC Copyright © Cengage Learning. All rights reserved 22
- 23. Section 4.5 The Sign and Magnitude of Ionic Charge 3. Elements in Group IVA occupy unique positions relative to the noble gases (could gain or lose four electrons). Return to TOC Copyright © Cengage Learning. All rights reserved 23
- 24. Section 4.5 The Sign and Magnitude of Ionic Charge Isoelectronic Species • A series of ions/atoms containing the same number and configuration of electrons. O2-, F-, Ne, Na+, Mg2+, and Al3+ 1s22s22p6 Return to TOC Copyright © Cengage Learning. All rights reserved 24
- 25. Section 4.5 The Sign and Magnitude of Ionic Charge Isoelectronic Species Mg2+ and Ne Return to TOC Copyright © Cengage Learning. All rights reserved 25
- 26. Section 4.5 The Sign and Magnitude of Ionic Charge Concept Check Choose an alkali metal, an alkaline earth metal, a noble gas, and a halogen so that they constitute an isoelectronic series when the metals and halogen are written as their most stable ions. • What is the electron configuration for each species? • Determine the number of electrons for each species. • Determine the number of protons for each species. Return to TOC Copyright © Cengage Learning. All rights reserved 26
- 27. Section 4.6 Lewis Structures for Ionic Compounds Formation of an Ionic Compound • Ion formation requires the presence of two elements: – A metal that can donate electrons. – A nonmetal that can accept electrons. • The electrons lost by the metal are the same ones gained by the nonmetal. • The positive and negative ions simultaneously formed from such electron transfer attract one another. Return to TOC Copyright © Cengage Learning. All rights reserved 27
- 28. Section 4.6 Lewis Structures for Ionic Compounds Lewis Structure • Combination of Lewis symbols that represents either the transfer or the sharing of electrons in chemical bonds. Return to TOC Copyright © Cengage Learning. All rights reserved 28
- 29. Section 4.6 Lewis Structures for Ionic Compounds The Reaction Between Sodium and Chlorine Return to TOC Copyright © Cengage Learning. All rights reserved 29
- 30. Section 4.6 Lewis Structures for Ionic Compounds The Reaction Between Sodium and Oxygen Return to TOC Copyright © Cengage Learning. All rights reserved 30
- 31. Section 4.6 Lewis Structures for Ionic Compounds The Reaction Between Calcium and Chlorine Return to TOC Copyright © Cengage Learning. All rights reserved 31
- 32. Section 4.7 Chemical Formulas for Ionic Compounds • Ionic compounds are always neutral; no net charge is present. • The ratio in which positive and negative ions combine is the ratio that achieves charge neutrality for the resulting compound. Return to TOC Copyright © Cengage Learning. All rights reserved 32
- 33. Section 4.7 Chemical Formulas for Ionic Compounds Writing Chemical Formulas for Ionic Compounds 1. The symbol for the positive ions is always written first. 2. The charges on the ions that are present are not shown in the formula. 3. The subscripts in the formula give the combining ratio for the ions. Return to TOC Copyright © Cengage Learning. All rights reserved 33
- 34. Section 4.7 Chemical Formulas for Ionic Compounds Example • Compound formed between Li+ and O2– – Need two Li+ to balance out the 2- charge on oxygen. • Formula is Li2O. Return to TOC Copyright © Cengage Learning. All rights reserved 34
- 35. Section 4.7 Chemical Formulas for Ionic Compounds Concept Check Determine the chemical formula for the compound that is formed when each of the following pairs of ions interact. Ba2+ and Cl– BaCl2 Fe3+ and O2– Fe2O3 Pb4+ and O2– PbO2 Return to TOC Copyright © Cengage Learning. All rights reserved 35
- 36. Section 4.8 The Structure of Ionic Compounds Solid Ionic Compounds • Consists of positive and negative ions arranged in such a way that each ion is surrounded by nearest neighbors of the opposite charge. • Any given ion is bonded by electrostatic attractions to all the other ions of opposite charge immediately surrounding it. Return to TOC Copyright © Cengage Learning. All rights reserved 36
- 37. Section 4.8 The Structure of Ionic Compounds Sodium Chloride (NaCl) Return to TOC Copyright © Cengage Learning. All rights reserved 37
- 38. Section 4.8 The Structure of Ionic Compounds Formula Unit • Smallest whole-number repeating ratio of ions present in an ionic compound that results in charge neutrality. • Chemical formulas for ionic compounds represent the simplest ratio of ions present. Return to TOC Copyright © Cengage Learning. All rights reserved 38
- 39. Section 4.8 The Structure of Ionic Compounds Cross-Section of NaCl Return to TOC Copyright © Cengage Learning. All rights reserved 39
- 40. Section 4.9 Recognizing and Naming Binary Ionic Compounds Naming Compounds • Binary Compounds: Composed of two elements Ionic and covalent compounds included • Binary Ionic Compounds: Metal-nonmetal Metal is always present as the positive ion, and the nonmetal is always present as the negative ion. Return to TOC Copyright © Cengage Learning. All rights reserved 40
- 41. Section 4.9 Recognizing and Naming Binary Ionic Compounds Naming Ionic Compounds • The full name of the metallic element is given first, followed by a separate word containing the stem of the nonmetallic element name and the suffix –ide. Return to TOC Copyright © Cengage Learning. All rights reserved 41
- 42. Section 4.9 Recognizing and Naming Binary Ionic Compounds Names of Selected Common Nonmetallic Ions Return to TOC Copyright © Cengage Learning. All rights reserved 42
- 43. Section 4.9 Recognizing and Naming Binary Ionic Compounds Examples KCl Potassium chloride MgBr2 Magnesium bromide CaO Calcium oxide Return to TOC Copyright © Cengage Learning. All rights reserved 43
- 44. Section 4.9 Recognizing and Naming Binary Ionic Compounds Naming Ionic Compounds (for Metals with Variable Charges) • Metals in these compounds form more than one type of positive charge. • Charge on the metal ion must be specified. • Roman numeral indicates the charge of the metal cation (positively charged ion). • Transition metal cations usually require a Roman numeral. Return to TOC Copyright © Cengage Learning. All rights reserved 44
- 45. Section 4.9 Recognizing and Naming Binary Ionic Compounds Examples CuBr Copper(I) bromide FeS Iron(II) sulfide PbO2 Lead(IV) oxide Return to TOC Copyright © Cengage Learning. All rights reserved 45
- 46. Section 4.9 Recognizing and Naming Binary Ionic Compounds Metallic Elements with a Fixed Ionic Charge Return to TOC Copyright © Cengage Learning. All rights reserved 46
- 47. Section 4.9 Recognizing and Naming Binary Ionic Compounds Exercise Name each of the following compounds: K2S potassium sulfide Fe2O3 iron(III) oxide CoCl2 cobalt(II) chloride Return to TOC Copyright © Cengage Learning. All rights reserved 47
- 48. Section 4.10 Polyatomic Ions Polyatomic Ion • Ion formed from a group of atoms (held together by covalent bonds) through loss or gain of electrons. Return to TOC Copyright © Cengage Learning. All rights reserved 48
- 49. Section 4.10 Polyatomic Ions Polyatomic Ions • Must be memorized (see Table 4.3 on pg. 99 in text). • Examples of compounds containing polyatomic ions: NaOH Sodium hydroxide Mg(NO3)2 Magnesium nitrate (NH4)2SO4 Ammonium sulfate Return to TOC Copyright © Cengage Learning. All rights reserved 49
- 50. Section 4.10 Polyatomic Ions Generalizations • Most of the polyatomic ions have a negative charge. • Two of the negatively charged polyatomic ions, OH– and CN–, have names ending in –ide and the rest of them have names ending in either – ate or –ite. Return to TOC Copyright © Cengage Learning. All rights reserved 50
- 51. Section 4.10 Polyatomic Ions Generalizations • A number of –ate, –ite pairs of ions exist. The – ate ion always has one more oxygen atom than the –ite ion. Both the –ate and –ite ions of a pair carry the same charge. • A number of pairs of ions exist wherein one member of the pair differs from the other by having a hydrogen atom present. In such pairs, the charge on the ion that contains hydrogen is always 1 less than that on the other ion. Return to TOC Copyright © Cengage Learning. All rights reserved 51
- 52. Section 4.11 Chemical Formulas and Names for Ionic Compounds Containing Polyatomic Ions • Determined in the same way as those for ionic compounds that contain monatomic ions. • The positive and negative charges present must add to zero. Na+ and OH– form NaOH. Mg2+ and NO3– form Mg(NO3)2. NH4+ and SO42– form (NH4)2SO4. Return to TOC Copyright © Cengage Learning. All rights reserved 52
- 53. Section 4.11 Chemical Formulas and Names for Ionic Compounds Containing Polyatomic Ions Exercise Which of the following compounds is named incorrectly? • KNO3 potassium nitrate • TiO2 titanium(II) oxide • Sn(OH)4 tin(IV) hydroxide • (NH4)2SO3 ammonium sulfite • CaCrO4 calcium chromate titanium(IV) oxide Return to TOC Copyright © Cengage Learning. All rights reserved 53
Editor's Notes
- #13: Ca: 2 valence electrons (4s 2 ) Se: 6 valence electrons (4s 2 4p 4 ) C: 4 valence electrons (2s 2 2p 2 )
- #20: When potassium loses an electron, there are 19 protons and 18 electrons. Therefore, 19p + + (-18e - ) = +1. The ion is K + . When sulfur gains two electrons, there are 16 protons and 18 electrons. Therefore, 16p + + (-18e - ) = -2. The ion is S 2- .
- #27: One example could be: K + , Ca 2+ , Ar, and Cl - The electron configuration for each species is 1s 2 2s 2 2p 6 3s 2 3p 6 . The number of electrons for each species is 18. K + has 19 protons, Ca 2+ has 20 protons, Ar has 18 protons, and Cl - has 17 protons.
- #36: BaCl 2 Fe 2 O 3 PbO 2
- #48: potassium sulfide iron(III) oxide cobalt(II) chloride
- #54: The correct answer is “b”. The charge on oxygen is -2. Since there are two oxygen atoms, the overall charge is -4. Therefore, the charge on titanium must be +4 (not +2 as the Roman numeral indicates).