2. Electron Transfer Dot Structures Ionic Compounds

3. Keeping Track of Electrons l The electrons responsible for the chemical properties of atoms are those in the outer energy level.

4. Keeping Track of Electrons l Atoms in the same column have the same valence electrons. l Easily found by looking up the group number on the periodic table.

5. 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

6. 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.

7. Write the electron dot diagram for l Na l Mg lClC lOlO lFlF l Ne l He

8. Electron Dots For Cations l Metals will have few valence electrons Ca

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

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

11. Electron Dots For Anions l Nonmetals will have many valence electrons. l They will gain electrons to fill outer shell. P P -3

12. Stable Octets l All atoms react to achieve noble gas configuration. l 8 valence electrons. l Also called the octet rule. Ar

13. Ionic Bonding l The bond is formed through the transfer of electrons. l Electrons are transferred to achieve noble gas configuration. l Anions and cations are held together by opposite charges.

14. Ionic Bonding NaCl

15. Ionic Bonding Na Cl + -

16. Counting Electrons During the formation of an ionic compound the total number of electrons lost (by cations) must equal the total number of electrons gained (by anions).

17. Ionic Bonding l All the electrons must be accounted for, total lost = total gained! CaP

18. Ionic Bonding CaP

19. Ionic Bonding Ca +2 P

20. Ionic Bonding Ca +2 P Ca

21. Ionic Bonding Ca +2 P -3 Ca

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

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

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

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

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

27. Ionic Bonding Ca P P +2 -3

28. Ionic Bonding Ca 3 P 2 Formula Unit