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MYP Chemistry Ionic Bonding and Ionic Compounds

MYP Chemistry Ionic Bonding and Ionic Compounds. International College Spain. Electron Configuration in Ionic Bonding. OBJECTIVES: Use the periodic table to infer the number of valence electrons in an atom, and draw it’s electron dot structure. Electron Configuration in Ionic Bonding.

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MYP Chemistry Ionic Bonding and Ionic Compounds

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  1. MYP ChemistryIonic Bonding and Ionic Compounds International College Spain

  2. Electron Configuration in Ionic Bonding • OBJECTIVES: • Use the periodic table to infer the number of valence electrons in an atom, and draw it’s electron dot structure.

  3. Electron Configuration in Ionic Bonding • OBJECTIVES: • Describe the formation of cations (positive ions) from metals, and of anions (negative ions) from non-metals.

  4. Valence Electrons • The electrons responsible for the chemical properties of atoms are those in the outer energy level. • Valence electrons - The electrons in the outer energy level or shell • the highest occupied energy level • Inner electrons -those in the energy levels below.

  5. Keeping Track of Electrons • Atoms in the same column... • Have the same outer electron configuration. • Have the same valence electrons. • Easily found: same as the main group number on the periodic table. • Group 2A: Be, Mg, Ca, etc. • 2 valence electrons

  6. Electron Dot diagrams • A way of keeping track of valence electrons. • How to write them? • Write the symbol. • Put one dot for each valence electron • Don’t pair up until they have to. X

  7. The Electron Dot diagram for Nitrogen • Nitrogen has 5 valence electrons. • First we write the symbol. N • Then add 1 electron at a time to each side. • Until they are forced to pair up.

  8. Write electron dot diagrams: • Na • Mg • C • O • F • Ne

  9. Electron Configurations for Cations • Metals lose electrons to attain noble gas configuration. • They make positive ions (cations) • If we look at the electron configuration, it makes sense to lose electrons: • Na 2,8,1 1 valence electron • Na+2,8 noble gas configuration

  10. Electron Dots For Cations • Metals will have few valence electrons (usually 3 or less) Ca

  11. Electron Dots For Cations • Metals will have few valence electrons • These will come off Ca

  12. Electron Dots For Cations • Metals will have few valence electrons • These will come off • Forming positive ions Ca2+ Pseudo-noble gas configuration Now make Sc an ion.

  13. Electron Configurations for Anions • Nonmetals gain electrons to attain noble gas configuration. • They make negative ions (anions) • Halide ions- ions from chlorine or other halogens that gain electrons • S 1s22s22p63s23p4 6 valence electrons • S2-1s22s22p63s23p6 noble gas configuration.

  14. Electron Dots For Anions • Nonmetals will have many valence electrons (usually 5 or more) • They will gain electrons to fill outer shell. P P3-

  15. Stable Electron Configurations • All atoms react to achieve noble gas configuration. • Noble gases have 8 outer shell (valence) electrons. • Also called the octet rule. Ar

  16. Ionic Bonds The characteristics of an ionic bond. Ions held together by…….. electrostatic attraction

  17. Ionic Bonds • Characteristics of ionic compounds • electrical conductors when melted and when in aqueous solution. • High m.p. • Brittle, hard crystals

  18. Properties of ionic compounds • You are provided with three ionic compounds • For each carry out the following tests • Heat a sample strongly in a test tube. • Add a spatula of the compound to 25 cm3 of water in a small beaker- stir • Test the conductivity of the solution Repeat using two spatulas

  19. Ionic Bonding • Anions and cations are held together by opposite charges. • Ionic compounds are called salts. • Simplest ratio is called the formula unit. • The bond is formed through the transfer of electrons. • Electrons are transferred to achieve noble gas configuration.

  20. Ionic Bonding Na Cl

  21. Ionic Bonding Na+ Cl-

  22. Ionic Bonding • All the electrons must be accounted for Ca P

  23. Ionic Bonding Ca P

  24. Ionic Bonding Ca2+ P

  25. Ionic Bonding Ca2+ P Ca

  26. Ionic Bonding Ca2+ P 3- Ca

  27. Ionic Bonding Ca2+ P 3- Ca P

  28. Ionic Bonding Ca2+ P 3- Ca2+ P

  29. Ionic Bonding Ca Ca2+ P 3- Ca2+ P

  30. Ionic Bonding Ca Ca2+ P 3- Ca2+ P

  31. Ionic Bonding Ca2+ Ca2+ P 3- Ca2+ P 3-

  32. Ionic Bonding = Ca3P2 Formula Unit Calcium Phosphide

  33. Classwork problems (a) Show the bonding between the following • Magnesium and Oxygen • Potassium and Chlorine • Calcium and Fluorine • Lithium and Nitrogen • Aluminium and Fluorine

  34. Homework problems These are slightly harder • Magnesium and Phosphorus • Beryllium and Nitrogen • Calcium and Sulphur • Magnesium and Nitrogen • Aluminium and Oxygen

  35. Properties of Ionic Compounds • Crystalline structure, usually solids • A regular repeating arrangement of ions in the solid • Ions are strongly bonded together. • Structure is rigid. • High melting points • Electrical conductors when melted • Electrical conductors in solution

  36. Crystalline structure

  37. Do they Conduct? • Conducting electricity is allowing charges to move. • In a solid, the ions are locked in place. • Ionic solids are insulators. • When melted, the ions can move around. • Melted ionic compounds conduct. • NaCl: must get to about 800 ºC. • Dissolved in water they conduct (aqueous)

  38. Bonding in Metals • OBJECTIVES: • Use the theory of metallic bonds to explain the physical properties of metals.

  39. Bonding in Metals • OBJECTIVES: • Describe the arrangements of atoms in some common metallic crystal structures.

  40. Metallic Bonds • How atoms are held together in the solid. • Metals hold on to their valence electrons very weakly. • Think of them as positive ions (cations) floating in a sea of electrons:

  41. + + + + + + + + + + + + Sea of Electrons • Electrons are free to move through the solid. • Metals conduct electricity.

  42. Metals are Malleable • Hammered into shape (bend). • Also ductile - drawn into wires. • Both malleability and ductility explained in terms of the mobility of the valence electrons

  43. + + + + + + + + + + + + Malleable

  44. + + + + + + + + + + + + Malleable • Electrons allow atoms to slide by.

  45. + - + - - + - + + - + - - + - + Ionic solids are brittle

  46. - + - + - + - + + - + - - + - + Ionic solids are brittle • Strong Repulsion breaks crystal apart.

  47. Crystalline structure of metal • If made of one kind of atom, metals are among the simplest crystals • Body-centered cubic: • every atom has 8 neighbors • Na, K, Fe, Cr, W

  48. Crystalline structure of metal 2. Face-centered cubic: • every atom has 12 neighbors • Cu, Ag, Au, Al, Pb 3. Hexagonal close-packed • every atom also has 12 neighbors • different pattern due to hexagonal • Mg, Zn, Cd

  49. Alloys • We use lots of metals every day, but few are pure metals • Alloys - mixtures of 2 or more elements, at least 1 is a metal • made by melting a mixture of the ingredients, then cooling • Brass: an alloy of Cu and Zn • Bronze: Cu and Sn

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