2. MYP Chemistry Ionic Bonding and Ionic Compounds International College Spain

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

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

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

6. Keeping Track of Electrons l Atoms in the same column... –Have the same outer electron configuration. –Have the same valence electrons. l Easily found: same as the main group number on the periodic table. l Group 2: Be, Mg, Ca, Sr, Ba. –2 valence electrons

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

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

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

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

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

12. Electron Dots For Cations l Metals will have few valence electrons l These will come off l Forming positive ions Ca 2+ noble gas configuration

13. Electron Configurations for Anions l Nonmetals gain electrons to attain noble gas configuration. l They make negative ions (anions) l Halide ions- ions from chlorine or other halogens that gain electrons l S (2,8,6) - 6 valence electrons l S 2- (2,8,8) - a noble gas configuration.

14. Electron Dots For Anions l Nonmetals will have many valence electrons (usually 5 or more) l They will gain electrons to fill outer shell. P P 3-

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

16. Ionic Bonding  Between metals and non-metals  Transfer of electrons  Full outer shells  Oppositely charged ions created  Ions held to one another by electrostatic attraction  Giant structure formed

17. Ionic Bonds Characteristics of ionic compounds l Usually soluble in water l Electrical conductors when molten and when in aqueous solution. l High m.p. l Brittle, hard crystals

18. Properties of ionic compounds l You are provided with three ionic compounds l For each carry out the following tests 1. Heat a sample strongly in a test tube. 2. Add a spatula of the compound to 25 cm 3 of water in a small beaker- stir 3. Test the conductivity of the solution Repeat using two spatulas

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

20. Ionic Bonding NaCl

21. Ionic Bonding Na + Cl -

22. Ionic Bonding l All the electrons must be accounted for CaP

23. Ionic Bonding CaP

24. Ionic Bonding Ca 2+ P

25. Ionic Bonding Ca 2+ P Ca

26. Ionic Bonding Ca 2+ P 3- Ca

27. Ionic Bonding Ca 2+ P 3- Ca P

28. Ionic Bonding Ca 2+ P 3- Ca 2+ P

29. Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

30. Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

31. Ionic Bonding Ca 2+ P 3- Ca 2+ P 3- Ca 2+

32. Ionic Bonding = Ca 3 P 2 Formula Unit Calcium Phosphide

33. Classwork problems (a) Show the bonding between the following 1. Magnesium and Oxygen 2. Potassium and Chlorine 3. Calcium and Fluorine 4. Lithium and Nitrogen 5. Aluminium and Fluorine

34. Homework problems These are slightly harder 6. Magnesium and Phosphorus 7. Beryllium and Nitrogen 8. Calcium and Sulphur 9. Magnesium and Nitrogen 10. Aluminium and Oxygen

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

36. Crystalline structure

37. Conducting electricity l Conducting electricity is allowing charges to move. l In a solid, the ions have charges but are locked in place. l Ionic solids are insulators. l When melted, the charged ions can move around. Melted ionic compounds conduct electricity. –To melt NaCl, it must get to about 800 ºC. l Dissolved in water (aqueous) the ions are now free to move and they conduct electricity.

38. Ionic solids are brittle +-+- + - +- +-+- + - +-

39. + - + - + - +- +-+- + - +- l Displacing the top layer (diagram) puts ions of the same charge near one another creating strong repulsion that breaks the crystal apart.

40. Solubility l Ionic solids are often (but not always) soluble in water. l Solubility usually (but not always) increases with increasing temperature. l Solution animation Solution animation