Ionic bonding

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Ionic bonding

  1. 1. CHAPTER 6 Ionic Bonding © 2013 Marshall Cavendish International (Singapore) Private Limited 1
  2. 2. Chapter 6 Ionic Bonding 6.1 The Stable Electronic Configuration of a Noble Gas 6.2 Forming Ions 6.3 Ionic Bond: Transferring Electrons 6.4 Chemical Formulae of Ionic Compounds 6.5 Structure and Physical Properties of Ionic Compounds 2
  3. 3. 6.1 The Stable Electronic Configuration of a Noble Gas Learning Outcome At the end of this section, you should be able to: • describe the stable electronic configuration of a noble gas. 3
  4. 4. 6.1 The Stable Electronic Configuration of a Noble Gas What are Noble Gases? • Elements that belong to Group 0 of the Periodic Table • Examples: He, Ne, Ar, Kr and Rn • Atoms of noble gases are stable and unreactive. • They exist in nature as single atoms. 4
  5. 5. 6.1 The Stable Electronic Configuration of a Noble Gas What is the Noble Gas Structure? • Noble gases have full or complete outer shells. Helium has a duplet configuration (2 outer electrons). All other noble gases have an octet configuration (8 outer electrons). 5
  6. 6. 6.1 The Stable Electronic Configuration of a Noble Gas Why Do Atoms React? • Atoms of most other elements are reactive because they do not have the noble gas structure (i.e. their outer shells are not fully-filled). • Atoms of these elements lose, gain or share outer electrons to attain the noble gas configuration and form compounds. 6
  7. 7. 6.1 The Stable Electronic Configuration of a Noble Gas Chemical Bonding Atoms gain or lose electrons to attain noble gas configuration Ionic bonding Atoms share electrons to attain noble gas configuration Covalent bonding 7
  8. 8. Chapter 6 Ionic Bonding 6.1 The Stable Electronic Configuration of a Noble Gas 6.2 Forming Ions 6.3 Ionic Bond: Transferring Electrons 6.4 Chemical Formulae of Ionic Compounds 6.5 Structure and Physical Properties of Ionic Compounds 8
  9. 9. 6.2 Forming Ions Learning Outcome At the end of this section, you should be able to: • describe the formation of positive ions (cations) and negative ions (anions) to achieve the noble gas configuration. 9
  10. 10. 6.2 Forming Ions What is an Ion? Recall: Atoms have an equal number of protons and electrons. They are electrically neutral. • An atom loses or gains electrons to form ions. • Ions are charged particles. No. of electrons ≠ No. of protons 10
  11. 11. 6.2 Forming Ions What is an Ion? • • Positively-charged ions are called cations. • URL Ions can be positively- or negatively-charged. Negatively-charged ions are called anions. 11
  12. 12. 6.2 Forming Ions Formation of Cations • Atoms of metals lose electrons to form positively-charged ions called cations. •In this way, they achieve the noble gas configuration. 12
  13. 13. 6.2 Forming Ions Example 1: Formation of sodium (Na+) ion Na atom Electronic configuration: 2, 8, 1 Number of protons = 11 Number of electrons = 11 The Na atom loses one outer electron to form the Na+ ion. Why? To achieve stable octet (noble gas) configuration. Neon (2, 8) 13
  14. 14. 6.2 Forming Ions Example 1: Formation of sodium (Na+) ion 2, 8 2, 8, 1 sodium atom loses one outer electron Na atom: 11p, 12n, 11e Charge = 11p + 11e = (+11) + (–11) =0 Neutral Na atom + Na+ ion: 11p, 12n, 10e Charge = 11p + 10e = (+11) + (–10) = +1 Positively-charged Na+ ion 14
  15. 15. 6.2 Forming Ions Example 2: Formation of calcium (Ca2+) ion 2, 8, 8 2, 8, 8, 2 calcium atom loses two outer electrons Ca atom: 20p, 20n, 20e Charge = 20p + 20e = 20(+1) + 20(–1) = (+20) + (–20) = 0 Neutral Ca atom 2+ Ca2+ ion: 20p, 20n, 18e Charge = 20p + 18e = 20(+1) + 18(–1) = (+20) + (–18) = +2 Positively-charged Ca2+ ion 15
  16. 16. 6.2 Forming Ions Common Cations and Their Charges Metal Ion Formula of ion sodium sodium ion Na+ potassium potassium ion K+ calcium calcium ion Ca2+ magnesium magnesium ion Mg2+ aluminium aluminium ion Al3+ 16
  17. 17. 6.2 Forming Ions Formation of Anions • Atoms of non-metals gain electrons to form negatively-charged ions called anions. •In this way, they achieve the noble gas configuration. 17
  18. 18. 6.2 Forming Ions Example 1: Formation of chloride (Cl–) ion Cl atom Electronic configuration: 2, 8, 7 Number of protons = 17 Number of electrons = 17 What happens in the formation of a chloride ion? The chlorine atom gains one electron in its outer shell to achieve a stable octet (noble gas) configuration. Argon (2, 8, 8) 18
  19. 19. 6.2 Forming Ions Example 1: Formation of chloride (Cl–) ion 2, 8, 7 2, 8, 8 chlorine atom gains one electron Cl atom: 17p, 18n, 17e Charge = 17p + 17e = (+17) + (–17) =0 Neutral Cl atom Cl– ion: 17p, 18n, 18e Charge = 17p + 18e = (+17) + (–18) = –1 Negatively charged Cl– ion 19
  20. 20. 6.2 Forming Ions Example 2: Formation of oxide (O2–) ion 2, 6 oxygen atom gains two electrons 2, 8 2– O atom: 8p, 8n, 8e O2– ion: 8p, 8n, 10e Charge = 8p + 8e = (+8) + (–8) =0 Charge = 8p + 10e = (+8) + (–10) = –2 Neutral O atom Negatively charged O2– ion 20
  21. 21. 6.2 Forming Ions Common Anions and Their Charges Non-metal Ion Formula of ion chlorine chloride ion Cl– bromine bromide ion Br– oxygen oxide ion O2– sulfur sulfide ion S2– 21
  22. 22. Why do metals lose electrons to form positive ions (cations) but non-metals gain electrons to form negative ions (anions)? 22
  23. 23. Chapter 6 Ionic Bonding 6.1 The Stable Electronic Configuration of a Noble Gas 6.2 Forming Ions 6.3 Ionic Bond: Transferring Electrons 6.4 Chemical Formulae of Ionic Compounds 6.5 Structure and Physical Properties of Ionic Compounds 23
  24. 24. 6.3 Ionic Bond: Transferring Electrons Learning Outcome At the end of this section, you should be able to: • describe how an ionic bonds are formed between metals and non-metals. 24
  25. 25. 6.3 Ionic Bond: Transferring Electrons Ionic Bonding • Ionic bonds are formed between metals and non-metals. Examples: Group VII: Fluorine, chlorine Group VI: Oxygen, sulfur Examples: Group I: Sodium, potassium Group II: Magnesium, calcium • This is done through the transfer of electron(s) from metals to non-metals. 25
  26. 26. 6.3 Ionic Bond: Transferring Electrons Ionic Bonding Metallic atom loses electron(s) Non-metallic atom gains electron(s) Positive ion Negative ion (cation) (anion) electrostatic forces of attraction (hold oppositely charged ions together) 26
  27. 27. 6.3 Ionic Bond: Transferring Electrons Formation of Ionic Compound Example 1: Sodium chloride Step 1: Formation of Positive Ions Each sodium atom (Na) loses its single outer electron to form a positively-charged sodium ion (Na+). Na 2, 8, 1 Na+ + e− 2, 8 27
  28. 28. 6.3 Ionic Bond: Transferring Electrons Step 2: Formation of Negative Ions Each chlorine atom gains an electron from a sodium atom to form a negatively-charged chloride ion (Cl−). Cl 2, 8, 7 + e− Cl – 2, 8, 8 28
  29. 29. 6.3 Ionic Bond: Transferring Electrons Step 3: Formation of Ionic Bonds Loses one electron Sodium atom 2, 8, 1 Gains one electron Chlorine atom 2, 8, 7 Electrostatic forces of attraction Sodium ion Chloride ion 2, 8, 8 2, 8 Sodium and chlorine react in the ratio of 1 : 1 to form sodium chloride (NaCl). URL 29
  30. 30. 6.3 Ionic Bond: Transferring Electrons Example 2: Magnesium chloride Magnesium atom loses two electrons. Chlorine atoms gain one electron each. Chloride ion Magnesium Chloride ion 2, 8, 8 2, 8, 8 ion 2, 8 Magnesium reacts with chlorine in the ratio of 1 : 2 to form magnesium chloride (MgCl2). 30
  31. 31. Chapter 6 Ionic Bonding 6.1 The Stable Electronic Configuration of a Noble Gas 6.2 Forming Ions 6.3 Ionic Bond: Transferring Electrons 6.4 Chemical Formulae of Ionic Compounds 6.5 Structure and Physical Properties of Ionic Compounds 31
  32. 32. 6.4 Chemical Formulae of Ionic Compounds Learning Outcome At the end of this section, you should be able to: • deduce the chemical formula of an ionic compound from the charges on the ions and vice versa. 32
  33. 33. 6.4 Chemical Formulae of Ionic Compounds Chemical Formulae of Ionic Compounds • The formula of an ionic compound is constructed by balancing the charges on the positive and negative ions. • All the positive charges must equal all the negative charges in an ionic compound. 33
  34. 34. 6.4 Chemical Formulae of Ionic Compounds Example: Magnesium oxide Oxygen forms O2− ions. Magnesium forms Mg2+ ions. Mg2+ O2− Charge: +2 Charge: −2 Since 1 × (+2 charge) balances out 1 × (−2 charge), The formula is MgO. 34
  35. 35. 6.4 Chemical Formulae of Ionic Compounds Example: Copper(II) hydroxide Copper ion Hydroxide ion Cu2+ Charge: +2 OH− Charge: −1 To balance the charges, multiply the smaller charge (−1) by 2 to make it equal to +2. Since 1 × (+2 charge) balances out 2 × (−1 charge), The formula is Cu(OH)2. 35
  36. 36. 6.4 Chemical Formulae of Ionic Compounds Example 1 Write the chemical formula of aluminium oxide. oxide ion aluminium ion Al 3 + O 2− Charge: −2 Charge: +3 Al2O3 Therefore, the formula is Al2O3. 36
  37. 37. 6.4 Chemical Formulae of Ionic Compounds Example 2 Write the chemical formula of calcium carbonate. calcium ion Ca 2 + carbonate ion CO3 2 − Charge: +3 Ca2(CO3)2 Charge: −2 CaCO3 Since ‘2’ is a common factor, it can be removed. Therefore, the formula is CaCO3. URL 37
  38. 38. Chapter 6 Ionic Bonding 6.1 The Stable Electronic Configuration of a Noble Gas 6.2 Forming Ions 6.3 Ionic Bond: Transferring Electrons 6.4 Chemical Formulae of Ionic Compounds 6.5 Structure and Physical Properties of Ionic Compounds 38
  39. 39. 6.5 Structure and Physical Properties of Ionic Compounds Learning Outcomes At the end of this section, you should be able to: • state that ionic compounds form giant lattice structures; • deduce the formulae of ionic compounds from their lattice structures; • relate the physical properties of ionic compounds to their lattice structures. 39
  40. 40. 6.5 Structure and Physical Properties of Ionic Compounds Structure of Ionic Compounds Ionic compounds form giant ionic structures. Also known as giant lattice structures or crystal lattices Consist of an endlessly repeating three-dimensional lattice of positive and negative ions Ions are closely packed, arranged in an orderly manner and held in place by ionic bonds 40
  41. 41. 6.5 Structure and Physical Properties of Ionic Compounds Structure of NaCl Sodium chloride crystal Three-dimensional arrangement of sodium ions and chloride ions Sodium ions and chloride ions alternate with each other. 41
  42. 42. 6.5 Structure and Physical Properties of Ionic Compounds Structure of NaCl Strong forces of attraction between ions in crystal lattice Na+ Cl – Na+ Cl– A large amount of energy is required to overcome these forces of attraction between ions. Cl– Na+ Na+ Cl– Na + Na+ Cl– Cl– Na+ Na+ Cl– Cl– Na+ Cl – Cl– Na+ Na+ Cl– Na+ Cl – Na + Na+ Cl– Cl– Cl– Na+ Na Na+ Cl– + Na+ Cl– Cl– Na+ Na+ Cl– Na+ Cl– Na+ Cl– Cl– Na+ Cl– Na+ Cl– Na+ 42
  43. 43. 6.5 Structure and Physical Properties of Ionic Compounds Structure of NaCl Cl− ion Each chloride ion is surrounded by six sodium ions. Na+ ion Each sodium ion is surrounded by six chloride ions. The ratio of sodium ions to chloride ions is 1 : 1. Hence, the formula unit of sodium chloride is NaCl. 43
  44. 44. 6.5 Structure and Physical Properties of Ionic Compounds Melting and Boiling Points of Ionic Compounds • High melting and boiling points Na+ Cl – Na+ • Non-volatile Cl– Cl– Na+ Na+ Cl– Na + Na+ Cl– • Exist as solids at room temperature Cl– Na+ Na+ Cl– Cl– Na+ Cl – Cl– Na+ Na+ Cl– Na+ Cl– Na + Na+ Cl– Cl– Cl– Na+ Na Na+ Cl– + Na+ Cl– Cl– Na+ Na+ Cl– Na+ Cl– Na+ Cl– Cl– Na+ Cl– Na+ Cl– Na+ 44
  45. 45. 6.5 Structure and Physical Properties of Ionic Compounds Solubility of Ionic Compounds • Usually soluble in water Cl– Na+ Cl– Na+ Cl – Na + Cl dissolve in water Na+ – Na+ Cl– Na+ Na+ Water molecules • URL Cl– Usually insoluble in organic solvents E.g. ethanol, turpentine, petrol 45
  46. 46. 6.5 Structure and Physical Properties of Ionic Compounds Electrical Conductivity of Ionic Compounds solid NaCl aqueous NaCl molten NaCl 46
  47. 47. 6.5 Structure and Physical Properties of Ionic Compounds Electrical Conductivity of Ionic Compounds • Ionic compounds conduct electricity in the molten and aqueous states. • They do not conduct electricity in the solid state. • In the molten and aqueous states, mobile ions are present. • Mobile ions conduct electricity. 47
  48. 48. Chapter 6 Ionic Bonding Concept Map 48

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