Copy of G8_Topic 7-9_Chemical Bonding (1).pptx

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1. Academic Year 2024/2025 Pearson Edexcel IGCSE Level Grade 8 Unit 1 Principles of Chemistry Topic 7-9: Chemical Bonding (book pages 75-100)

2. Topic 7 Ionic Bonding (pages 30-35) Learning Objectives : Understand how ions are formed from electron loss or gain Know the charges of ions: Draw dot-and-cross diagrams Understand the properties of ionic compounds

3. (Recall) Metals and Non-metals

4. (Recall) The Arrangement of electrons in an atom The electrons move around the nucleus in a series of levels called energy levels or shells .

5. (Recall) Electronic Configuration Atomic number = number of protons = number of electrons (2,1) (2,2) (2,3) (2,4) Element Li Be B C Atomic number 3 4 5 6 The arrangement of electrons in an atom is called its electronic configuration .

6. (Recall) Electron Configuration and the Periodic Table Elements in the same group in the Periodic Table have the same number of electrons in their outer shell.

7. Ionic Bonding Ionic Bonding is an electrostatic force of attraction between oppositely charged ions. Ionic compounds usually contain a metal and a non-metal. For example: sodium chloride, NaCl

8. Ionic Bonding Ionic Bonding is an electrostatic force of attraction between oppositely charged ions. Ionic compounds usually contain a metal and a non-metal. For example: sodium chloride, NaCl A metal atom loses electron forming a positive ion is called a cation . For example: sodium ion, Na + A non-metal atom gains electron forming negative ion is called an anion . For example: chloride ion, Cl -

9. Ionic Bond Formation in Sodium Chloride, NaCl

10. Ionic Bonding Metals lose electrons to form positive ions or cations Other metals to familiarise:

11. Ionic Bonding Non-metals gain electrons to form negative ions or anions. The nonmetals’ name ending is changed with ‘ ide ’ For example: When nitrogen atom gains 3 electrons it will be called a nitride ion .

12. Ionic Bonding

13. Ionic Bonding

14. Ionic Bonding

15. The charges of ions

16. The charges of ions

17. The charges of ions

18. The charges of ions

19. Giant Ionic Lattice/Structure

20. Physical Properties of Ionic Compounds High melting and boiling points Crystalline solids Brittle Soluble in water but insoluble in organic solvent Conducts electricity in the aqueous and molten state but not in the solid state

21. Physical Properties of Ionic Compounds Ionic crystals tend to be brittle . When external force/stress is applied, this will bring the ions with the same charge alongside each other. Like charges repel and the crystals split itself apart.

22. Electrolysis of Molten Ionic Compounds Electrolysis uses an electric current to split a compound into its elements. Passing an electric current through the molten salt in this cell is to decompose sodium chloride into its elements, sodium metal and chlorine gas. C l - ions that collide with the positive electrode ( anode ) loses electrons are oxidized to C l 2 gas Na + ions collide with the negative electrode ( cathode ), and gains electrons to form sodium metal

23. Topic 8 Covalent Bonding (pages 85-96) Learning Objectives : Understand how covalent bond is formed between atoms by sharing a pair of electrons Understand how to use dot-and-cross diagrams to represent covalent molecules in diatomic molecules, in inorganic molecules and organic molecules Explain the physical properties of simple molecular and giant covalent structures Understand the term intermolecular forces between covalent molecules/compounds

24. What is a covalent bond Covalent Bonding is an electrostatic force of attraction between the nuclei of two atoms that make up a bond and the shared pair of electron

25. Covalent Bonding in Diatomic Molecules Diatomic molecules contain two atoms that are bonded together by covalent bonds. A dot-and-cross diagram is used show covalent bonds in molecules.

26. Covalent Bonding in a chlorine molecule, Cl 2 The ‘Octet Rule’

27. Covalent Bonding in hydrogen chloride, HCl

28. Covalent Bonding in methane, CH 4

29. Covalent Bonding in water, H 2 O

30. Covalent Bonding in ethane, C 2 H 6

31. Multiple Covalent Bonding Two pairs of electrons are shared between two oxygen atoms forming a double covalent bond (also called double bond ).

32. Multiple Covalent Bonding Three pairs of electrons are shared between two nitrogen atoms forming a triple covalent bond (also called triple bond ).

33. Multiple Covalent Bonding Covalent bonding in carbon dioxide, CO 2

34. Multiple Covalent Bonding Covalent bonding in ethene, C 2 H 4

35. Molecules where the central atom does not have 8 in its outer shell

36. Simple Molecular/Covalent Structures Substances with simple molecular/covalent structures: have weak force of attraction between molecules tend to be gases or liquids or solids with melting points and boiling points do not conduct electricity tend to be insoluble in water are often soluble in organic solvents

37. Simple Molecular Structures Melting point and boiling point increases as relative molecular mass increases

38. Simple Molecular/Covalent Structures Allotropes are forms of the same element. Diamond and graphite are allotropes of carbon Another allotrope of carbon is C 60 fullerene. It has a simple molecular structure C 60 fullerene

39. Giant Covalent Structures Substances with giant covalent structures: have strong covalent bonds have high melting and boiling points

40. Giant Covalent Structures: Diamond Diamond is a pure form of carbon. It has high melting and boiling points It is hard It does not conduct electricity

41. Giant Covalent Structures: Graphite Graphite is also a form of carbon. It has a layer structure like a pack of playing cards.

42. Giant Covalent Structures has a high melting and boiling points conducts electricity because it has delocalised/ free-moving electrons is soft/brittle material (although the bonds between atoms are strong, the force of attraction between layers is weak) Graphite

43. Topic 9 Metallic Bonding (pages 98-100) Learning Objectives : Know how to represent a metallic lattice in a 2D diagram Understand metallic bonding Explain the physical properties of metals

44. Metallic Bonding

45. Metallic Bonding Metallic bonding is the electrostatic forces of attraction between each positive ion and delocalised electrons.

46. Physical Properties of Metals metals conduct electricity because there are delocalised electrons that are free to move throughout the structure

47. Physical Properties of Metals good conductors of electricity in the solid and molten state good conductors of heat high melting point and boiling point malleable (can be flattened into thin sheets) ductile (can be drawn into wires)

48. Summary of Properties Type of Bond (type of elements) Structure Strength of Bond/ Force of attraction Melting/ Boiling Point Electrical conductivity Solubility in Water Example Ionic (usually metal & non-metal) Giant strong high good in molten and aqueous soluble NaCl Covalent (Non-metals) Simple weak force of attraction between molecules low poor/ non- conductor insoluble H 2 O, CO 2 , O 2 , N 2 , I 2 ,F 2 , NH 3 , C 60 Covalent (Non-metals) Giant strong high poor/ non- conductor (except graphite) insoluble diamond, graphite Metallic (Metals) Giant strong high good in solid and molten insoluble Copper, Cu

49. Quick Revision Covalent Bonds Ionic Bonds Metallic Bonds